Create mode

In Create mode the input file can be extremely simple. First, the geometry is trivial: one atom at the origin. Indeed, no coordinates etc. are read from input; any such items are ignored.

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 don't have to be looked after.

In Create mode you need only a one-line input file of the following form:

CREATE Atomtype Datafile

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 begin with the standard chemical symbol (H, He, Li, ...) of the element to be created. Optionally the name may have an suffix of the form .text. The suffix begins with a period (.); the part after the period (text) is at your discretion as long as it does not contain a delimiter. A few examples:

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 equivalent to and 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 very simple calculation as follows (the 'creation' of a Carbon atom);

$ADFBIN/adf << eor
 Create C.dzp
eor

The presence of the keyword create sets the computational mode of ADF to: create a basic atom. The argument (C.dzp) is then analyzed and found to have as initial part C, telling ADF that we'll be creating a Carbon atom. Since the file-specification part is missing, the data file with the basis set etc. must be the (local) file with the name C.dzp.

More often you will directly address a file (with the basis set) that is not local, but located in the database of your ADF package. The script could then be:

$ADFBIN/adf << eor
 Create C $ADFHOME/atomicdata/DZ/C.1s
eor

Here you address the file 'C.1s' in the database subdirectory DZ/ (this contains basis sets of double-zeta quality).

A considerable number of data files are included in the ADF database. To apply such a file for the creation of a basic atom:

Make a copy of the data file in the directory where you want to run the program. Since the standard data file names satisfy the requirements for atom type names you can now use the simplest option to use the create key:
Construct a one line input file in ( create name-of-data-file-copy )
Run ADF by typing
adf <in >out
When the calculation has finished, give the result file TAPE21 a suitable name and move it to a directory where you build your database of fragment libraries.
Examine logfile and out to check that everything has gone well.

You may want to define alternative basic atoms, different from those in the standard ADF database, for instance to try out a different basis set developed by yourself. By inspection of one of the standard data files you can see what the contents of such a file should be. A complete description is given in Appendix 1.

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 section Geometry in Chapter 2.3.