Basis sets and atomic fragments
*******************************

See also:

  * What basis set should I use in ADF?

  * Basis set file format


STO basis sets
==============

The basis functions used in ADF are commonly known as Slater-type
Orbitals (STOs). The ADF package comes with a database of STO basis
sets. The basis sets are simple ASCII files and they are located in
the directory "$AMSHOME/atomicdata/ADF". A description of the basis
set file format can be found in the appendix Basis set file format.

A basis set can roughly be characterized by its size (single-,
double-, triple-zeta; with or without polarization) and by the level
of frozen core approximation. The standard basis sets available in ADF
are:

* **SZ** Minimal basis sets: single-zeta without polarization. The
  exponents of the functions correspond to the standard STO-3g basis
  sets used in programs that employ Gaussian-type basis functions.
  Type-SZ files are provided only for the lighter elements, up to Kr.

* **DZ** Double-zeta basis sets without polarization functions. A
  triple-zeta set is used for the 3d shells of the first row
  transition metals, the 4f shells of the lanthanides, and the 5f
  shells of the actinides. In all these cases a double-zeta set
  provides a rather poor expansion basis for the true (numerically
  computed) atomic orbital.

* **DZP** Double-zeta polarized basis. The basis sets in DZP are
  derived from DZ, extended with a polarization function. This type of
  basis set is provided only for the elements up to Ar, and for the 4p
  series Ga through Kr.

* **TZP** Triple-zeta basis sets. A polarization function is added for
  H through Ar and for Ga through Kr (from DZP).

* **TZ2P** Triple-zeta with two polarization functions, for H through
  Ar and Ga through Kr (from DZP). Note that the TZ2P basis set files
  are provided only for the lighter elements, up to Kr. The ZORA/TZ2P
  basis set files are provided for all elements. Typically for all
  elements one polarization function is added compared to the
  corresponding TZP basis set. Note, however, that TZ2P will not
  always give you extra basis functions for most lanthanide and
  actinide frozen core basis sets.

In addition to the standard basis sets, the database contains
directories with special basis sets:

* **TZ2P+** For transition metals Sc-Zn and lanthanides (ZORA) only:
  as TZ2P, but with an extra d-STO (3d metals) or an extra f-STO
  (lanthanides, ZORA).

* **ZORA** contains basis sets designed for ZORA relativistic
  calculations (relativistic calculations have special basis set
  requirements, especially in the core region). ZORA basis sets with
  frozen core should be used **exclusively** in relativistic
  calculations with the ZORA approach, while all-electron ZORA basis
  sets can be used for both relativistic and non-relativistic
  calculations. The ZORA/QZ4P basis set can be loosely described as
  core triple zeta, valence quadruple zeta, with four sets of
  polarization functions.

* **ET** contains several even-tempered basis sets which enable one to
  go to the basis set limit, such as ET/ET-pVQZ, ET/ET-QZ3P, ET/ET-
  QZ3P-1DIFFUSE, ET/ET-QZ3P-2DIFFUSE, ET/ET-QZ3P-3DIFFUSE. The
  accuracy of the smallest basis set in this directory can loosely be
  described as quadruple zeta in the valence with three polarization
  functions added. This directory also contains basis sets with extra
  diffuse functions. In response calculations one should use such
  large basis sets in case of small molecules. Very diffuse functions
  are absolutely necessary to get good results for excitation energies
  corresponding to high-lying orbitals (Rydberg states).

* **AUG** contains several augmented standard basis sets which enable
  one to get reasonable results for excitation energies with
  relatively small basis sets, such as AUG/ASZ, AUG/ADZ, AUG/ADZP,
  AUG/ATZP, AUG/ATZ2P.

* **Corr** contains several extended all-electron ZORA basis sets,
  especially useful in MBPT (MP2, GW, BSE) calculations, Corr/TZ3P and
  Corr/QZ6P. For MBPT larger basis sets are needed to achieve the same
  accuracy as in a standard DFT calculation.

Furthermore, in "$AMSHOME/atomicdata/ADF" you will find:

* **Special/AE** contains non-relativistic basis sets for all-electron
  calculations. However, these files cannot be used as such, because
  they do not contain any fit sets. They serve as a starting point for
  the development of (new) basis sets. For some of the all-electron
  sets appropriate fit sets have already been generated. The
  corresponding database files can be found in the appropriate sub-
  directories SZ, DZ, DZP, et cetera.

* **Special/Vdiff** contains non-relativistic basis sets that include
  very diffuse functions. These were recommended for response
  calculations. Very diffuse functions are absolutely necessary to get
  good results for excitation energies corresponding to high-lying
  orbitals. Recommendation: use the even-tempered basis sets in the ET
  directory, since these basis sets are better.

* **Special/MDC** contains non-relativistic basis sets with optimized
  fit functions especially useful for accurate multipole-derived
  charges. These are available only for a limited number of basis
  sets.

The directory "$AMSHOME/atomicdata/Dirac" contains the input files for
the DIRAC auxiliary program (see the RELATIVITY keyword).

**Frozen core**

Multiple occurrences of one chemical element in the same basis set
sub-directory correspond to different levels of the frozen core
approximation. Manganese, for instance, may have a basis set for an
atom with a frozen 2p shell and another one with a frozen 3p shell.
The file names are self-explanatory: Mn.2p stands for a data file for
Manganese with frozen core shells up to the 2p level. An all-electron
basis set would correspond to a file that has no frozen-core suffix in
its name.

**Electronic-configuration-specific basis sets**

Another case in which one element occurs multiple times in one basis
set directory may be found when basis sets have been developed for
different electronic configurations: the Slater-type basis sets are
fitted to numerical orbitals from runs with different occupation
numbers. Currently this applies only for Ni (in
"$AMSHOME/atomicdata/ADF" "DZ", "TZP" and "TZ2P"), where basis sets
are supplied for the d8s2 and the d9s1 configurations respectively.
Since in earlier releases only the d8s2 variety was available, the
names of the basis set files are Ni.2p (for d8s2) and Ni_d9.2p, and
likewise Ni.3p and Ni_d9.3p.

**References on basis sets**

* E. van Lenthe and E.J. Baerends,  *Optimized Slater-type basis sets
  for the elements 1-118.*  Journal of Computational Chemistry 24,
  1142 (2003)

* D.P. Chong, E. van Lenthe, S.J.A. van Gisbergen and E.J. Baerends,
  *Even-tempered Slater-Type orbitals revisited: From Hydrogen to
  Krypton.*  Journal of Computational Chemistry 25, 1030 (2004)

* D.P. Chong, *Augmenting basis set for time-dependent density
  functional theory calculation of excitation energies: Slater-type
  orbitals for hydrogen to krypton.* Molecular Physics 103, 749 (2005)

Older references for STO basis sets are Refs. [1] [2] [3]. See also
the paper by Raffenetti on design and optimization of even-tempered
STO basis sets [4]. The paper by Chong describes completeness profiles
as a visual tool in estimating the completeness of a basis set [5].
Finally, Zeiss and coworkers [6] describe field-induced polarization
functions for STOs. These are useful for defining basis sets with
diffuse functions for (hyper)polarizability and other property
calculations.

The procedure for the use and optimization of fit functions is
described by Baerends et al. [7].

For documentation on how to make custom even-tempered basis/fit sets,
see the old ADF 2014 documentation.


Available basis sets
====================

ADF has optimized STO basis sets for the whole periodic table
(Z=1-120).

The following tables give an indication of which all-electron (ae) and
frozen core (fc) standard basis sets are available for the different
elements in ADF.


Available standard basis sets for non-relativistic (non-rel) and ZORA calculations H-Kr (Z=1-36)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+
| Element      | ae or fc     | SZ, DZ       | DZP          | TZP, TZ2P    | TZ2P+        | QZ4P, ET     | AUG          |
|==============|==============|==============|==============|==============|==============|==============|==============|
| H-He (Z=1-2) | ae           | Yes          | Yes          | Yes          |              | Yes          | Yes          |
+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+
| Li-Ne        | ae           | Yes          | Yes          | Yes          |              | Yes          | Yes          |
| (Z=3-10)     |              |              |              |              |              |              |              |
+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+
|              | .1s          | Yes          | Yes          | Yes          |              |              | non-rel      |
+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+
| Na-Ar        | ae           | Yes          | Yes          | Yes          |              | Yes          | Yes          |
| (Z=11-18)    |              |              |              |              |              |              |              |
+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+
|              | .1s .2p      | Yes          | Yes          | Yes          |              |              | non-rel      |
+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+
| K-Ca         | ae           | Yes          | Yes          | Yes          |              | Yes          | Yes          |
| (Z=19-20)    |              |              |              |              |              |              |              |
+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+
|              | .2p .3p      | Yes          | Yes          | Yes          |              |              | non-rel      |
+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+
| Sc-Zn        | ae           | Yes          |              | Yes          | Yes          | Yes          | Yes          |
| (Z=21-30)    |              |              |              |              |              |              |              |
+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+
|              | .2p .3p      | Yes          |              | Yes          | Yes          |              | non-rel      |
+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+
| Ga-Kr        | ae           | Yes          | Yes          | Yes          |              | Yes          | Yes          |
| (Z=31-36)    |              |              |              |              |              |              |              |
+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+
|              | .3p .3d      | Yes          | Yes          | Yes          |              |              | non-rel      |
+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+


Available standard basis sets for non-relativistic calculations Rb-Cm (Z=37-96)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

+-----------------------------------+-----------------------------------+-----------------------------------+
| Element                           | fc                                | DZ, TZP                           |
|===================================|===================================|===================================|
| Rb-Sr (Z=37-38)                   | .3p .3d  .4p                      | Yes                               |
+-----------------------------------+-----------------------------------+-----------------------------------+
| Y-Cd (Z=39-48)                    | .3d .4p                           | Yes                               |
+-----------------------------------+-----------------------------------+-----------------------------------+
| In-Ba (Z=49-56)                   | .4p .4d                           | Yes                               |
+-----------------------------------+-----------------------------------+-----------------------------------+
| La-Lu (Z=57-71)                   | .4d .5p                           | Yes                               |
+-----------------------------------+-----------------------------------+-----------------------------------+
| Hf-Hg (Z=72-80)                   | .4d .4f                           | Yes                               |
+-----------------------------------+-----------------------------------+-----------------------------------+
| Tl-Rn (Z=81-86)                   | .4d .4f .5p .5d                   | Yes                               |
+-----------------------------------+-----------------------------------+-----------------------------------+
| Fr-Ra (Z=87-88)                   | .5p .5d                           | Yes                               |
+-----------------------------------+-----------------------------------+-----------------------------------+
| Ac-Cm (Z=89-96)                   | .5d                               | Yes                               |
+-----------------------------------+-----------------------------------+-----------------------------------+


Available standard basis sets for ZORA calculations Rb-Og (Z=37-120)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

+----------------------+----------------------+----------------------+----------------------+----------------------+
| Element              | ae or fc             | DZ, TZP, TZ2P        | TZ2P+                | QZ4P                 |
|======================|======================|======================|======================|======================|
| Rb-Sr (Z=37-38)      | ae                   | Yes                  |                      | Yes                  |
+----------------------+----------------------+----------------------+----------------------+----------------------+
|                      | .3p .3d  .4p         | Yes                  |                      |                      |
+----------------------+----------------------+----------------------+----------------------+----------------------+
| Y-Cd (Z=39-48)       | ae                   | Yes                  |                      | Yes                  |
+----------------------+----------------------+----------------------+----------------------+----------------------+
|                      | .3d  .4p             | Yes                  |                      |                      |
+----------------------+----------------------+----------------------+----------------------+----------------------+
| In-Ba (Z=49-56)      | ae                   | Yes                  |                      | Yes                  |
+----------------------+----------------------+----------------------+----------------------+----------------------+
|                      | .4p  .4d             | Yes                  |                      |                      |
+----------------------+----------------------+----------------------+----------------------+----------------------+
| La-Yb (Z=57-70)      | ae                   | Yes                  | Yes                  | Yes                  |
+----------------------+----------------------+----------------------+----------------------+----------------------+
|                      | .4d  .5p             | Yes                  | Yes                  |                      |
+----------------------+----------------------+----------------------+----------------------+----------------------+
| Lu (Z=71)            | ae                   | Yes                  |                      | Yes                  |
+----------------------+----------------------+----------------------+----------------------+----------------------+
|                      | .4d  .5p             | Yes                  |                      |                      |
+----------------------+----------------------+----------------------+----------------------+----------------------+
| Hf-Hg (Z=72-80)      | ae                   | Yes                  |                      | Yes                  |
+----------------------+----------------------+----------------------+----------------------+----------------------+
|                      | .4d  .4f             | Yes                  |                      |                      |
+----------------------+----------------------+----------------------+----------------------+----------------------+
| Tl    (Z=81)         | ae                   | Yes                  |                      | Yes                  |
+----------------------+----------------------+----------------------+----------------------+----------------------+
|                      | .4d  .4f .5p         | Yes                  |                      |                      |
+----------------------+----------------------+----------------------+----------------------+----------------------+
| Pb-Rn (Z=82-86)      | ae                   | Yes                  |                      | Yes                  |
+----------------------+----------------------+----------------------+----------------------+----------------------+
|                      | .4d  .4f .5p .5d     | Yes                  |                      |                      |
+----------------------+----------------------+----------------------+----------------------+----------------------+
| Fr-Ra (Z=87-88)      | ae                   | Yes                  |                      | Yes                  |
+----------------------+----------------------+----------------------+----------------------+----------------------+
|                      | .5p .5d              | Yes                  |                      |                      |
+----------------------+----------------------+----------------------+----------------------+----------------------+
| Ac-Lr (Z=89-103)     | ae                   | Yes                  |                      | Yes                  |
+----------------------+----------------------+----------------------+----------------------+----------------------+
|                      | .4f .5d              | Yes                  |                      |                      |
+----------------------+----------------------+----------------------+----------------------+----------------------+
| Rf-Cn (Z=104-112)    | ae                   | Yes                  |                      | Yes                  |
+----------------------+----------------------+----------------------+----------------------+----------------------+
|                      | .4f .5d .5f          | Yes                  |                      |                      |
+----------------------+----------------------+----------------------+----------------------+----------------------+
| Nh-Og (Z=113-118)    | ae                   | Yes                  |                      | Yes                  |
+----------------------+----------------------+----------------------+----------------------+----------------------+
|                      | .5d .5f              | Yes                  |                      |                      |
+----------------------+----------------------+----------------------+----------------------+----------------------+
| Uue-Ubn (Z=119-120)  | ae                   | Yes                  |                      | Yes                  |
+----------------------+----------------------+----------------------+----------------------+----------------------+
|                      | .5f                  | Yes                  |                      |                      |
+----------------------+----------------------+----------------------+----------------------+----------------------+

For heavier elements, from Rb on, the non-relativistic all-electron
basis sets are missing. In the ZORA basis sets directory you will find
all-electron basis sets for all elements (Z = 1-120), which also could
be used in non-relativistic calculations. Note, however, that these
basis sets were optimized for ZORA calculations, which means that non-
relativistic calculations will not always give you the expected
accuracy. Non-relativistically optimized basis sets for the heavier
elements are provided in a separate directory AE, which contains basis
sets of single-, double- and triple-zeta quality indicated
respectively by suffixes 'sz', 'dz', and 'tz'. The files in
Special/AE/ are not complete basis set files, because they don't
contain fit sets (the usage and relevance of fit functions is
explained later).

**Basis sets directories**

Basis sets can be found in the directory "$AMSHOME/atomicdata/ADF".
For non-relativistic calculations they are in the sub-directories SZ,
DZ, DZP, TZP, TZ2P, TZ2P+. For ZORA calculations they are in ZORA/SZ,
ZORA/DZ, ZORA/DZP, ZORA/TZP, ZORA/TZ2P, ZORA/TZ2P+, ZORA/TZ2P-J,
ZORA/QZ4P, ZORA/QZ4P-J. The augmented basis sets are in AUG/ASZ,
AUG/ADZ, AUG/ADZP, AUG/ATZP, AUG/ATZ2P. The even tempered basis sets
are in ET/ET-pVQZ, ET/ET-QZ3P, ET/ET-QZ3P-1DIFFUSE, ET/ET-QZ3P-
2DIFFUSE, ET/ET-QZ3P-3DIFFUSE. The basis sets for MBPT calculations
are in Corr/TZ3P, Corr/QZ6P. All-electron basis sets can be used in
non-relativistic and ZORA calculations.

**Basis sets acronyms**

* SZ:   single zeta

* DZ:   double zeta

* DZP:  double zeta + 1 polarization function

* TZP:  valence triple zeta + 1 polarization function

* TZ2P: valence triple zeta + 2 polarization functions

* TZ2P+: = TZ2P + extra d (3d metals) or extra f (lanthanides)

* QZ4P: valence quadruple zeta + 4 polarization functions,
  relativistically optimized

* ET: even tempered

  * pVQZ, QZ3P: valence quadruple zeta + 3 polarization functions,
    even tempered

  * QZ3P-nD: = QZ3P + n diffuse sets of s, p, d, and f functions, even
    tempered

* AUG: augmented

  * ASZ, ADZ, ADZP, ATZP, ATZ2P: augmented for use in TDDFT

* Corr: for use in MBPT

  * TZ3P: = all-electron (Z=1-54) ZORA/TZ2P + extra tight polarization
    function

  * QZ6P: = all-electron (Z=1-118) ZORA/QZ4P + extra tight
    polarization functions

* TZ2P-J, QZ4P-J: for use in ESR hyperfine or NMR spin-spin couplings

  * TZ2P or QZ4P + extra tight (mainly 1s) functions

**All-electron or frozen core**

* element name (without suffix): all-electron

* .1s frozen: 1s

* .2p frozen: 1s 2s 2p

* .3p frozen: 1s 2s 2p 3s 3p

* .3d frozen: 1s 2s 2p 3s 3p 3d

* .4p frozen: 1s 2s 2p 3s 3p 3d 4s 4p

* .4d frozen: 1s 2s 2p 3s 3p 3d 4s 4p 4d

* .4f frozen: 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f

* .5p frozen: 1s 2s 2p 3s 3p 3d 4s 4p 4d 5s 5p (La-Lu)

* .5p frozen: 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p (other)

* .5d frozen: 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d

* .6p frozen: 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 6s 6p (Ac-Lr)

* .5f frozen: 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f 6s 6p


The Basis Key
=============

The basis set can be specified in the input via the "Basis" key block.
The most important subkeys are Type and Core. Description of all
subkeys:

   Basis
      Type [...]
      Core [None | Small | Large]
   End

"Basis"
   Type:
      Block

   Description:
      Definition of the basis set

   "Type"
      Type:
         Multiple Choice

      Default value:
         DZ

      Options:
         [SZ, DZ, DZP, TZP, TZ2P, QZ4P, TZ2P-J, QZ4P-J, mTZ2P,
         AUG/ASZ, AUG/ADZ, AUG/ADZP, AUG/ATZP, AUG/ATZ2P, ET/ET-pVQZ,
         ET/ET-QZ3P, ET/ET-QZ3P-1DIFFUSE, ET/ET-QZ3P-2DIFFUSE, ET/ET-
         QZ3P-3DIFFUSE, Corr/TZ3P, Corr/QZ6P, Corr/ATZ3P, Corr/AQZ6P,
         POLTDDFT/DZ, POLTDDFT/DZP, POLTDDFT/TZP]

      GUI name:
         Basis set

      Description:
         Select the basis set to use.                      SZ: Single
         Z                      DZ: Double Z                      DZP:
         Double Z, 1 polarization function                      TZP:
         Triple Z, 1 polarization function                      TZ2P:
         Triple Z, 2 polarization functions                      QZ4P:
         Quad Z, 4 pol functions, all-electron
         AUG: Augmented (extra diffuse functions)
         ET: Even tempered all electron basis sets
         J: Extra tight functions                      These
         descriptions are meant to give an indication of the quality,
         but remember that ADF uses Slater type functions.
         For standard calculations (energies, geometries, etc.) the
         relative quality is:                      SZ < DZ < DZP < TZP
         < TZ2P < ET-pVQZ < QZ4P                      The basis set
         chosen will apply to all atom types in your molecule. If no
         matching basis set is found, ADF will try to use a basis set
         of better quality.                      For TDDFT
         applications and small negatively charged atoms or molecules,
         use basis sets with extra diffuse functions.
         J: TZ2P-J, QZ4P-J: for use in ESR hyperfine or NMR spin-spin
         couplings.                      Use the Basis panel to select
         a basis set per atom type, and to see what basis set actually
         will be used.

   "Core"
      Type:
         Multiple Choice

      Default value:
         Large

      Options:
         [None, Small, Large]

      GUI name:
         Frozen core

      Description:
         Select the size of the frozen core you want to use.
         Small and Large will be interpreted within the basis sets
         available (of the selected quality), and might refer to the
         same core in some cases.                      If you specify
         'None' you are guaranteed to have an all-electron basis set.

**Warning:** Do not include the Corepotentials keys when using the
Basis key. Typically one should not include both the Basis key and the
Fragments key.

Description of the other Basis subkeys:

   Basis
      CreateOutput Yes/No
      Path string
      PerAtomType
         Core [None | Small | Large]
         File string
         Symbol string
         Type [...]
      End
      PerRegion
         Core [None | Small | Large]
         File string
         Region string
         Type [...]
      End
      FitType [...]
   End

"Basis"
   "CreateOutput"
      Type:
         Bool

      Default value:
         No

      Description:
         If true, the output of the atomic create runs will be printed
         to standard output. If false, it will be saved to the file
         CreateAtoms.out in the AMS results folder.

   "Path"
      Type:
         String

      Description:
         The name of an alternative directory with basis sets to use.
         ADF looks for appropriate basis sets only within this
         directory. Default $AMSRESOURCES/ADF.

   "PerAtomType"
      Type:
         Block

      Recurring:
         True

      Description:
         Defines the basis set for all atoms of a particular type.

      "Core"
         Type:
            Multiple Choice

         Options:
            [None, Small, Large]

         Description:
            Size of the frozen core.

      "File"
         Type:
            String

         Description:
            The path of the basis set file (the path can either
            absolute or relative to $AMSRESOURCES/ADF). Note that one
            should include ZORA in the path for relativistic
            calculations, for example 'ZORA/QZ4P/Au'. Specifying the
            path to the basis file explicitly overrides the automatic
            basis file selection via the Type and Core subkeys.

      "Symbol"
         Type:
            String

         Description:
            The symbol for which to define the basis set.

      "Type"
         Type:
            Multiple Choice

         Options:
            [SZ, DZ, DZP, TZP, TZ2P, QZ4P, TZ2P-J, QZ4P-J, mTZ2P,
            AUG/ASZ, AUG/ADZ, AUG/ADZP, AUG/ATZP, AUG/ATZ2P, ET/ET-
            pVQZ, ET/ET-QZ3P, ET/ET-QZ3P-1DIFFUSE, ET/ET-QZ3P-
            2DIFFUSE, ET/ET-QZ3P-3DIFFUSE, Corr/TZ3P, Corr/QZ6P,
            Corr/ATZ3P, Corr/AQZ6P, POLTDDFT/DZ, POLTDDFT/DZP,
            POLTDDFT/TZP]

         Description:
            The basis sets to be used.

   "PerRegion"
      Type:
         Block

      Recurring:
         True

      Description:
         Defines the basis set for all atoms in a region. If
         specified, this overwrites the values set with the Basis%Type
         and Basis%PerAtomType keywords for atoms in that region. Note
         that if this keyword is used multiple times, the chosen
         regions may not overlap.

      "Core"
         Type:
            Multiple Choice

         Default value:
            Large

         Options:
            [None, Small, Large]

         Description:
            Size of the frozen core.

      "File"
         Type:
            String

         Description:
            The path of the basis set file (the path can either
            absolute or relative to $AMSRESOURCES/ADF). Note that one
            should include ZORA in the path for relativistic
            calculations, for example 'ZORA/QZ4P/Au'. Specifying the
            path to the basis file explicitly overrides the automatic
            basis file selection via the Type and Core subkeys.

      "Region"
         Type:
            String

         Description:
            The identifier of the region for which to define the basis
            set. Note that this may also be a region expression, e.g.
            'myregion+myotherregion' (the union of two regions).

      "Type"
         Type:
            Multiple Choice

         Default value:
            DZ

         Options:
            [SZ, DZ, DZP, TZP, TZ2P, QZ4P, TZ2P-J, QZ4P-J, mTZ2P,
            AUG/ASZ, AUG/ADZ, AUG/ADZP, AUG/ATZP, AUG/ATZ2P, ET/ET-
            pVQZ, ET/ET-QZ3P, ET/ET-QZ3P-1DIFFUSE, ET/ET-QZ3P-
            2DIFFUSE, ET/ET-QZ3P-3DIFFUSE, Corr/TZ3P, Corr/QZ6P,
            Corr/ATZ3P, Corr/AQZ6P, POLTDDFT/DZ, POLTDDFT/DZP,
            POLTDDFT/TZP]

         Description:
            The basis sets to be used.

   "FitType"
      Type:
         Multiple Choice

      Default value:
         Auto

      Options:
         [Auto, SZ, DZ, DZP, TZP, TZ2P, QZ4P, TZ2P-J, QZ4P-J, AUG/ASZ,
         AUG/ADZ, AUG/ADZP, AUG/ATZP, AUG/ATZ2P, ET/ET-pVQZ, ET/ET-
         QZ3P, ET/ET-QZ3P-1DIFFUSE, ET/ET-QZ3P-2DIFFUSE, ET/ET-QZ3P-
         3DIFFUSE]

      GUI name:
         STO fit set

      Description:
         Expert option.                      Select the auxiliary fit
         to be used for STOfit or old Hartree-Fock RI scheme.
         The fit set for a given atom is taken from the all-electron
         basis set file for the specified choice, for the same element
         as the atom.                      By default (Auto) the fit
         set is taken from the original basis set file.

For an example where you can use regions to define basis sets for
parts of your system, see Example: Multiresolution.


Automatic mode
==============

The following input will run a geometry optimization on water, using
an (almost) minimal input:

   "$AMSBIN/ams" <<eor
      Task GeometryOptimization
      System
         Atoms
            O  0  0  0
            H  1  1  0
            H -1  1  0
         End
         Symmetrize Yes
      End

      Engine ADF
         Basis
            Type TZP
         End
      EndEngine
   eor

* The "ATOMS" sub-block in the "System" block specifies the geometry
  of the system;

* the "Task GeometryOptimization" key instructs AMS to perform a
  geometry optimization;

* the "Basis" key instructs ADF to run the *create runs*
  automatically, using a TZP basis set.

The *automatic mode* will be used when the "Basis" key is present in
the input, or if no "Fragments" block key is present.

In *automatic mode* ADF will first create fragment files for all the
basic atom fragments found in the "Atoms" block. Normally this means
that for each atom type in your molecule a fragment file will be
created.

You may want to have different fragments using the same atomic
fragment. In AMS2026, this is less straightforward than in earlier
releases, because the dot notation that could be used for this is no
longer supported. For example, using "H.1" and "H.2" is not allowed in
AMS2026. An alternative may be the use of different regions or the use
of explicit atomic fragments.

In case of a relativistic calculation, the DIRAC program will also be
run automatically, and the create runs will include the correct
relativistic key and corresponding basis sets. For **ZORA**
calculations, ADF first tries to locate a special ZORA basis set. If
this does not succeed it will use a normal basis set if the required
basis set does not use a frozen core.


Create mode
===========

Expert option. In Create mode the input file is relatively simple.
First, the geometry is trivial: one atom at the origin.

Second, the problem is computationally so simple that default settings
for precision aspects, such as convergence criteria and levels of
numerical integration accuracy, are internally defined to be much more
stringent than in normal calculations. These aspects do not need to be
specified explicitly. Also one should specify the desired XC
functional. If you use the Basis key all this will be handled
automatically.

In Create mode you need an input file of the following form:

   System
     Atoms
       Atomtype 0 0 0
     End
   end
   Task SinglePoint
   Engine ADF
     CREATE Atomtype Datafile
   EndEngine

"Create"
   is the keyword. The remainder of the record (atomtype datafile) is
   the argument.

"Atomtype"
   is a name for the basic atom that you want to create. The program
   reads and interprets this name. Therefore, the name must be the
   standard chemical symbol (H, He, Li, ...) of the element to be
   created, or in case of ghost atoms Gh.name. Note that starting from
   AMS2026 it may no longer be appended with .text. Thus the dot
   notation is no longer supported: using, for example, "Mn.3" or "Cu
   .dz-new" will cause errors in AMS2026. A few examples:


Examples of appropriate and inappropriate atom type names used with the keyword Create.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

+----------------------------------------------------+----------------------------------------------------+
| **appropriate names**                              | **inappropriate names**                            |
+----------------------------------------------------+----------------------------------------------------+
| K                                                  | Si-with-core (not a chemical symbol)               |
+----------------------------------------------------+----------------------------------------------------+
| C                                                  | $HOME/atomicdata/ADF/DZ/C (not a chemical symbol)  |
+----------------------------------------------------+----------------------------------------------------+
| Gh.C                                               | Gh.C.dz (dot notation no longer allowed)           |
+----------------------------------------------------+----------------------------------------------------+
|                                                    | Sodium (Sodium is not the *symbol* for this        |
|                                                    | element (Na))                                      |
+----------------------------------------------------+----------------------------------------------------+
|                                                    | Li.newbasis (dot notation no longer allowed)       |
+----------------------------------------------------+----------------------------------------------------+

"Datafile"
   specifies the data file that contains the basis set and related
   items. It may contain a full path if the file does not reside in
   the working directory of the job. The Datafile part is optional. If
   you omit it, ADF assumes that the file name is identical to the
   atom type name, i.e. "Create Atomtype" is interpreted as "Create
   Atomtype Atomtype". In view of the restrictions that apply to the
   atom type name, the option to use the short form can only be used
   if the file name has the appropriate format. To make the input file
   easier to understand for a human reader you may, for Datafile, also
   type file=Datafile, where file= must be typed as such, and Datafile
   is the name of the file.

So you could have a simple calculation as follows (the 'creation' of a
Carbon atom):

   $AMSBIN/ams << eor
     System
       Atoms
         C 0 0 0
       End
     end
     Task SinglePoint
     Engine ADF
       Create C $AMSHOME/atomicdata/ADF/DZ/C.1s
     EndEngine
   eor

The presence of the keyword "create" sets the computational mode of
ADF to: *create a basic atom*. Here a basis set file is located in
"$AMSHOME/atomicdata/ADF", where the file 'C.1s' is located in the
sub-directory DZ (this contains basis sets of double-zeta quality).
Examine logfile and the output of this calculation to check that
everything has gone well.

A considerable number of basis set files are included in ADF. You can
also create basic atoms corresponding to so-called *Alternative
Elements*, with for instance a non-integer nuclear charge or a
different mass. See the next section.


Ghost Atoms, Non-standard Chemical Elements
===========================================

The atom type names used under atoms (and in the create record) must
begin with the standard chemical element symbol (H, He, Li...). The
program uses this to deduce the nuclear charge and other elemental
properties.

For the standard elements one can redefine the atomic mass (for
instance to define a suitable isotope). Masses are specified by adding
the desired mass (in Dalton) at the end of the atom's line (mass=).

It is also possible to define an artificial chemical element with
user-specified properties. Such new elements are denoted *Alternative
Elements*, and may for instance have a non-integer nuclear charge.

The chemical symbol for a (ghost) atom that has zero nuclear charge is
Gh. The "BASIS" key recognizes elements denoted with Gh.atom in the
ATOMS key as being ghost atoms. If one does not specifically select a
basis set for this ghost atom, the all-electron basis set for the atom
is selected in the creation of the ghost atom using the type of basis
set chosen with the BASIS key. The atom name must be the standard one-
or two-character symbol for the chemical element: Gh.H, Gh.He, Gh.Li,
and so on. Note that starting from AMS2026 it may no longer be
appended with .text. For example, using Gh.Mn.3 or Gh.Cu.dz-new will
cause errors in AMS2026. An alternative to this dot notation for
naming ghost atoms may be the use of different regions.

For other alternative elements, for instance that have a non-integer
nuclear charge, one should use one of the standard chemical symbols.
The "BASIS" key will use this chemical symbol for selecting the basis
set for this alternative element. Nuclear charges are specified by
adding the nuclear charge at the end of the atom's line
(nuclear_charge=).

You can create Gh-type basic atoms and other alternative elements and
use them subsequently as fragments in a molecule.


Automatic mode
--------------

AMS allows you to set user-defined masses for particular atoms. This
can be used to simulate isotopes of different atoms. Masses are
specified by adding the desired mass (in Dalton) at the end of the
atom's line.

**Example:** three different hydrogen isotopes:

   System
      Atoms
         N       0.000000    0.000000    0.010272
         H      -0.471582   -0.816803    0.407861
         H       0.943163    0.000000    0.407861 mass=2.014101778
         H      -0.471582    0.816803    0.407861 mass=3.01604927
      End
   End

**Use as fragment**

Alternative basic atoms can be used like any other basic atoms to
build up larger fragments and molecules. Gh can be considered just one
more chemical symbol along with the other traditional ones. For other
alternative elements one should define the nuclear charge, and
possibly the nuclear mass.

You may have different alternative elements in a molecule, with
different nuclear charges for instance.

**Example:** ghost atoms:

   System
      atoms
         Gh.O  -0.525330     -0.050971     -0.314517
         Gh.H  -0.942007      0.747902      0.011253
         Gh.H   0.403697      0.059786     -0.073568
         O      2.316633      0.045501      0.071858
         H      2.684616     -0.526577      0.749387
         C      2.781638     -0.426129     -1.190301
         H      2.350821      0.224965     -1.943415
         H      3.867602     -0.375336     -1.264613
         H      2.453296     -1.445999     -1.389381
      end
   end

**Example:** alternative elements:

   System
      Atoms
         Mg 0.0  0.0  0.0
         F  1.0  1.0  1.0  nuclear_charge=9.5
         F  1.0 -1.0 -1.0  nuclear_charge=9.5
         F -1.0  1.0 -1.0  nuclear_charge=9.5
         F -1.0 -1.0  1.0  nuclear_charge=9.5
      End
   End


Nuclear Model
=============

By default in ADF a point charge model is used for the nuclear charge
distribution. Alternatively, one can use a spherical Gaussian nuclear
charge distribution model, see Ref. [8]. Nuclear finite size effects
can have large effects on hyperfine interactions (ESR A-tensor, NMR
spin-spin coupling) if heavy atoms like, for example, Mercury (Hg),
are involved. In Ref. [8] it was asserted that the isotropic
J-couplings (parameters in NMR spin-spin coupling) are typically
reduced in magnitude by about 10 to 15 % for couplings between one of
the heaviest NMR nuclei and a light atomic ligand, and even more so
for couplings between two heavy atoms. This Ref. [8] gives more
details on the parameters used in the Gaussian nuclear charge
distribution model. Note that one needs basis sets with very tight
functions to see any effect of using a finite size of the nucleus
instead of a point nucleus. Such basis sets can be found for all
elements in "$AMSRESOURCES/ZORA/TZ2P-J" and
"$AMSRESOURCES/ZORA/QZ4P-J", and for some elements in
"$AMSRESOURCES/ZORA/jcpl", which are basis sets especially designed
for ESR hyperfine and NMR spin-spin coupling calculations.

   NuclearModel [PointCharge | Gaussian]

"NuclearModel"
   Type:
      Multiple Choice

   Default value:
      PointCharge

   Options:
      [PointCharge, Gaussian]

   Description:
      Model for the nuclear charge distribution.                   To
      see effects from your choice you will need to use a basis set
      with extra steep functions. For example you can find these in
      the ZORA/TZ2P-J basis directory.

In the ADF output, parameters will be shown for the Gaussian nuclear
charge distribution if one includes the following in the input for
ADF:

   PRINT Nuclei

Starting from ADF2013, ADF also uses a finite distribution of the
nuclear magnetic dipole moment for the calculation of the A-tensor.

[1] E. Clementi, C. Roetti, *Roothaan-Hartree-Fock atomic
    wavefunctions: Basis functions and their coefficients for ground
    and certain excited states of neutral and ionized atoms, Z* \leq
    54, Atomic Data and Nuclear Data Tables 14, 177 (1974)

[2] A.D. McLean, R.S. McLean, *Roothaan-Hartree-Fock atomic wave
    functions Slater basis-set expansions for Z = 55-92*, Atomic Data
    and Nuclear Data Tables 26, 197 (1981)

[3] J.G. Snijders, P. Vernooijs, E.J. Baerends, *Roothaan-Hartree-
    Fock-Slater atomic wave functions: Single-zeta, double-zeta, and
    extended Slater-type basis sets for* _87 Fr-_103 Lr, Atomic Data
    and Nuclear Data Tables 26, 483 (1981)

[4] R.C. Raffenetti, *Even-tempered atomic orbitals. II. Atomic SCF
    wavefunctions in terms of even-tempered exponential bases*,
    Journal of Chemical Physics 59, 5936 (1973)

[5] D.P. Chong, *Completeness profiles of one-electron basis sets*,
    Canadian Journal of Chemistry 73, 79 (1995)

[6] G.D. Zeiss, W.R. Scott, N. Suzuki, D.P. Chong, S.R. Langhoff,
    *Finite-field calculations of molecular polarizabilities using
    field-induced polarization functions: second- and third-order
    perturbation correlation corrections to the coupled Hartree-Fock
    polarizability of* H_2 O, Molecular Physics 37, 1543 (1979)

[7] E.J. Baerends, D.E. Ellis and P. Ros, *Self-consistent molecular
    Hartree-Fock-Slater calculations I. The computational procedure*,
    Chemical Physics 2, 41 (1973)

[8] J. Autschbach, *Magnitude of Finite-Nucleus-Size Effects in
    Relativistic Density Functional Computations of Indirect NMR
    Nuclear Spin-Spin Coupling Constants*, ChemPhysChem 10, 2274
    (2009)
