4.11 Selecting orbitals and density matrices (

`ORBITAL`[`,`[`RECORD=`]*record*]
[`,`[`TYPE=`]*orbtype*]
[`,STATE=`*state*]
[`,SYM[METRY]=`*symmetry*]

[`,SPIN=`*spin*]
[`,MS2=`*ms2*]
[`,[N]ELEC=`*nelec*]
[`,SET=`*iset*]
[`,OVL`]
[`,NOCHECK`]
[`,IGNORE[_ERROR`]]

`DENSITY`[`,`[`RECORD=`]*record*]
[`,`[`TYPE=`]*dentype*]
[`,STATE[B]=`*stateb*]
[`,SYM[B]=`*symb*]
[`,SPIN[B]=`*spinb*]
[`,MS2[B]=`*ms2b*]
[`,STATEK=`*statek*]
[`,SYMK=`*symk*]
[`,SPINK=`*spink*]
[`,MS2K=`*ms2k*]
[`,[N]ELEC=`*nelec*]
[`,SET=`*iset*]

where the (optional) specifications can be used to select specific orbitals or densities, if several different orbital sets are stored in the same record. If a specification is not given, it is not checked and the last written set that fullfills all other criteria is used. The meaning of the individual specifications are as follows:

*orbtype*- Orbital type. This can be one of
`CANONICAL`: canonical or pseudo-canonical orbitals;`NATURAL`: natural orbitals;`LOCAL`: localized orbitals;`LOCAL(PM)`: localized Pipek-Mezey orbitals;`LOCAL(BOYS)`: localized Boys orbitals;`PROJECTED`: projected virtual orbitals used in local calculations.

Without further specification, the most recently computed orbitals of the specified type are used. If the orbital type is not specified, the program will try to find the most suitable orbitals automatically. For instance, in MRCI calculations`NATURAL`orbitals will be used preferentially if available; MRPT (CASPT2) calculations will first search for`CANONICAL`orbitals, and local calculations will first look for`LOCAL`orbitals. Therefore, in most cases the orbital type needs not to be specified. *state*- Specifies a particular state in the form . For instance,
2.1 refers to the second state in symmetry 1.
This can be used if density matrices or natural orbitals have been computed for different states in a
state-averaged CASSCF calculation.
If not given, the last written orbitals are used.
A state-averaged density can be selected using
`STATE=AV[ERAGED]`. The specification of is optional; it can also be defined using the`SYMMETRY`key. *dentype*- Density type. This can be one of
`CHARGE`: charge density;`SPIN`: UHF spin density;`TRANSITION`: transition density matrix;

The default is`CHARGE`. *symmetry*- Specifies a particular state symmetry. Alternatively, the
state symmetry can be specified using
`STATE`(see above). *spin*- Spin quantum number, i.e. 0 for singlet, 1/2 for doublet, 1 for triplet, etc.
Alternatively
`MS2`can be used. *ms2*- , i.e. 0 for singlet, 1 for doublet, 2 for triplet etc.
Alternatively,
`SPIN`can be used. *nelec*- Number of electrons.
*iset*- Set number of orbitals. The orbital sets are numbered in the order they are stored.

In some cases (e.g. in `MATROP`) transition density matrices can be specified. In this case
`STATEB`, `SYMB`, `MS2B`, `SPINB` refer to the bra state and
`STATEK`, `SYMK`, `MS2K`, `SPINK` refer to the ket state.
If bra and ket differ, `TYPE=TRANSITION` is implied, and `SYMMETRY` is automatically
set to the product symmetry of bra and ket. If
`STATEK`, `SYMK`, `MS2K`, `SPINK` are not given, they are assumed to be
equal to the corresponding bra quantities. See section 65 for examples.

If `OVL` is specified, the starting orbitals are obtained by maximizing the overlap with
previous orbitals. By default, this is used if the basis dimension of the previous orbitals
is different then the current one. If `OVL` is specified this procedure is used even if the basis
dimensions are the same, which is occasionally useful if the contraction scheme changed.

If `NOCHECK` is specified, some consistency checks for finding correct orbitals are skipped,
and error messages like "ORBITALS CORRESPOND TO DIFFERENT GEOMETRY" are ignored.

If `IGNORE_ERROR` is specified, MPn or triples calculations can be forced with
other than canonical orbitals. Note that this can lead to meaningless results!
Note that in MULTI `IGNORE_ERROR` must be given on the `START` directive,
since in this program `ORBITAL` is used to define the new orbitals.

If any of the above options are given, they must be obeyed strictly, i.e., the program aborts if the request cannot be fulfilled.

Examples:

ORBITAL,2100.2 !Use SCF orbitals ORBITAL,2140.2 !Use (state-averaged) MCSCF orbitals ORBITAL,2140.2,CANONICAL !use canonical MCSCF orbitals ORBITAL,2140.2,NATURAL,STATE=2.1 !use natural MCSCF orbitals for second state in sym. 1

molpro@molpro.net 2019-03-19