4.2.34. MOTRA

The program MOTRA is used to transform one- and two-electron integrals from AO to MO basis. It reads the one-electron file and the file of ordered and symmetry blocked two-electron integrals generated by SEWARD.

The two-electron integral transformation is performed one symmetry block at a time, as a series of four sequential one-index transformations. The process includes a sorting of the half transformed integrals prior to the second half transformation. This step is performed in core if there is space enough of memory available to keep one symmetry block of integrals. Otherwise the half transformed integrals are written out on an temporary file. The result of the transformation is two files, TRAONE and TRAINT which contain the transformed one- and two-electron integrals, respectively.

The one-electron transformation is performed for the kinetic integrals and the bare nuclei Hamiltonian. If there are frozen orbitals MOTRA replaces the bare nuclei Hamiltonian by an effective Fock operator, which incorporates the interaction between the frozen (core) electrons and the remaining electrons. In practice this means that in any subsequent calculation (for example MRCI, CPF or MBPT) the effect of the frozen orbitals is incorporated into the one-electron Hamiltonian, and these orbitals need not be explicitly accounted for. The total energy of the frozen electrons is added to the nuclear–nuclear repulsion energy and transferred from MOTRA to the subsequent program(s).

The two-electron transformation is performed from the list of ordered integrals generated by SEWARD (file ORDINT).

4.2.34.1. Dependencies

To run the program MOTRA successfully the one- and two-electron integrals are needed. In addition, a set of MO coefficients must be available. The latter may be obtained by any wave function optimization program.

4.2.34.2. Files

4.2.34.2.1. Input files

The following is a list of input files

ONEINT

One-electron integral file generated by SEWARD.

ORDINT*

Ordered two-electron integrals generated by SEWARD.

INPORB

If MO’s are read in formatted form.

JOBIPH

If molecular orbitals are read from a RASSCF interface.

In general, input orbitals are supplied in the form of a formatted ASCII file, but can also be taken directly from the binary interface file, JOBIPH, created by the RASSCF program. The selection in controlled by input options.

4.2.34.2.2. Output files

The program MOTRA creates two files: The first carries all basic information and a list of transformed one-electron integrals. The second file includes the transformed two-electron integrals.

The following is a list of output files

TRAONE

Auxiliary data and transformed one-electron integrals.

TRAINT*

Transformed two-electron integrals.

4.2.34.3. Input

This section describes the input to the MOTRA program in the Molcas program system. The input for each module is preceded by its name like:

&MOTRA

4.2.34.3.1. Compulsory keywords

The following keywords are compulsory.

LUMOrb

Specifies that the molecular orbitals are read from a formatted file produced by one of the wave function generating programs. Note that either of Lumorb or Jobiph should be specified. LUMORB is the default keyword. No additional input is required.

JOBIph

Specifies that the molecular orbitals are read from a RASSCF job interface file. MOTRA will in this case read the average orbitals. No additional input is required.

When natural orbitals from a RASSCF (or a state averaged CASSCF) calculation are to be used in MOTRA, they can be produced, or extracted from an existing JOBIPH file, by RASSCF, using keyword OUTOrbitals.

4.2.34.3.2. Optional keywords

There are a few useful optional keywords that can be specified. The following is a list

AUTO

This keyword specified automatic deletion of orbitals based on occupation numbers. The following line contain one threshold per symmetry, and all orbitals with occupation numbers smaller that the threshold will be deleted. If AUTO and DELEte are both specified, the larger number will be used.

DELEted

Specifies the number of virtual orbitals that are not to be used as correlating orbitals in the subsequent CI calculation. The last orbitals in each symmetry are deleted. The default is no deleted orbitals. One additional line with the number of deleted orbitals in each symmetry (free format).

FROZen

Specifies the number of doubly occupied orbitals that are left uncorrelated in subsequent correlation calculation(s). Additional orbitals can be frozen in these programs, but from an efficiency point of view it is preferable to freeze orbitals in the transformation. One additional line with the number of frozen orbitals in each symmetry (free format). For more details on freezing orbitals in MOTRA see the program description. The frozen orbitals are the first in each symmetry block. Default is to freeze the core (but not semi-core) orbitals.

ONEL

Specifies that only one-electron integrals are to be transformed. No additional input is required.

PRINt

Specifies the print level in the program. The default (1) does not print the orbitals that are used in the transformation, but they appear at print level 2. Beware of large print levels since vast amounts of output may be produced. The value is read from the line after the keyword, in free format.

RFPErt

Add a constant reaction field perturbation to the bare nuclei Hamiltonian. The perturbation is read from the file RUNOLD (if not present defaults to RUNFILE) and is the latest self consistent perturbation generated by one of the programs SCF or RASSCF.

CTONly

Specifies that Cholesky vectors are to be transformed without subsequent calculation of the two-el integrals. It requires as input one of the two following strings: “pqK” or “Kpq”, which indicate the storage format as L(pq,K) or L(K,pq), respectively. The former is the default option. Transformed vectors are stored in the files _CHMOT, one for each compound symmetry. Available only in combination with Cholesky or RI integral representation.

DIAGonal integrals

Activates the evaluation of the diagonal integrals in MO basis. Requires the keyword CTONly. The file DIAGINT is generated which contains these integrals.

TITLe

This keyword should be followed by exactly one title line.

4.2.34.3.3. Input example

&MOTRA
Title  =  Water molecule.
* Don't correlate 1s on oxygen
Frozen =  1 0 0 0
Lumorb