A block type key in which the required molecular orbitals are specified. The key can be repeated in input any number of times; all occurrences are read and applied.
Orbitals type (data) END
The argument of the orbitals key (type) must be scf (for the scf orbitals) or frag (for the fragment orbitals) or loc (for the localized molecular orbitals, see the ADF User's Guide).
The frag option is not operational in the present release.
In many data records in the ORBITALS block, as noted in the description of these data records, you may specify a HOMOLUMO range.
A HOMOLUMO range is the following:
{HOMO{{-}n}} {LUMO{{+}n}}
HOMO: the highest occupied orbital
HOMO-n, with n an integer: the highest (n+1) occupied orbitals
LUMO: the lowest virtual orbital
LUMO+n, with n an integer: the lowest (n+1) virtual orbitals.
The HOMO part, or the LUMO part, or both must be specified. The integer n with sign is always optional, and the sign is always optional (and has no meaning, it is intended to enhance readability).
Thus, as an example,
HOMO-1 LUMO+1
means a range of 4 orbitals: the two highest occupied ones, and the two lowest virtuals.
Each data record in the orbitals block must have either of the following formats:
1. the word alpha or beta.
This specifies that subsequent
records refer to spin-alpha or spin-beta orbitals respectively. In a restricted
calculation this has no meaning and beta must
not be specified.
alpha and/or beta may occur any
number of times in the orbitals
block. All records until the first occurrence of
alpha or beta are assumed to
refer to spin-alpha orbitals.
2. label n1, n2, n3, ...
label is one of the subspecies of the
point group symmetry used in the adf
calculation and n1 etc. are indices of
the molecular orbitals (in that subspecies) that are to be computed. This
format is meaningless and must not be used for the loc orbitals type, because
localized orbitals do not
(necessarily) belong anymore to a particular symmetry representation.
3. label HOMOLUMO
label is one of the subspecies of the
point group symmetry used in the calculation, the orbitals follow from the
HOMOLUMO range.
4. label occ or label virt
occ specifies all orbitals (in that
symmetry representation) up to and including the highest occupied one. virt specifies all orbitals above the
highest occupied one. In this context partially
occupied orbitals are considered occupied. Note carefully that if in a
particular symmetry representation an empty orbital is computed below the
highest occupied one in that same representation (excited state), that
particular empty one is included in the list of
occ.
Again, this format is meaningless and must therefore not be used for the loc type
of orbitals.
5. all occ or all virt or all HOMOLUMO
Specifies for each symmetry representation:
This form is not to be used for the LOC
type of orbitals. However, using this for
LOC will not result in an
error but will be interpreted as identical to the following format.
6. all
This format must be used only for the LOC type of orbitals and simply
means: all computed localized orbitals (irrespective of occupation numbers).
7. n1, n2, ...
a simple list of integer indices.
This format must be used only for the loc type of orbitals since no
reference is made to any symmetry representation. The indices refer of course
to the list of localized orbitals as computed by adf, see the User's Guide.
The default value used when the ORBITALS key is not present is:
Orbitals SCF All HOMO-1 LUMO+1 End
