expandmo

Module expandmo is used to expand molecular orbital from a small basis set into a large basis set and construct automated  MCSCF active space by Atomic Valence Active Space (AVAS) based on target atomic valence orbitals. This module can be used to generate initial guess orbital of a large basis set calculation from the converged orbital of a small basis set calculation. Also, the expanded orbital can be used in dual-basis calculation approaches. AVAS is proposed by Garnet Kin-Lic Chan et al.(JCTC, 13, 4063-4078, 2017.)

General keywords

Overlap

Overlap is used to expand molecular orbital from a small basis set into a large basis set.

MINBAS

set valence AO such as five 3d atomic orbitals as target atomic orbitals. example file is test086.inp

minbas

5

1Co|3D-2

1Co|3D-1

1Co|3D0

1Co|3D1

1Co|3D2

AOBAS

set valence AO such as five 3d atomic orbitals as target atomic orbitals. example file is test086.inp 10 - 14 are the number of target 3d OAO.

aobas

5

10 11 12 13 14

PXYZ

rotate each Pi planar fragment so that the new Pz is vertical to molecular plan. For example, there are two Pi fragments the first one has comprised 4 pz (which is the number of first p orbitals) AOs of 3 12 21 30, and the second one has 2 AOs of 41 52.

Pxyz

2

4 2

3 12 21 30

41 52

OAO

form all OAOs of the molecular system. For example:

$expandmo

oao

$end

AVAS

Atomic Valence Active Space (AVAS) is used to automated construction MCSCF active space by set atomic valence orbitals.

FOCK

Contract Fock matrix to valence OAO and diagonalize Fock(OAO,OAO) to obtain valence CMO or LMO (VCMO or VLMO) and automated selection of active space. Notice that this method only supports AOBAS.

OCCAO

Set valence OAO occupied alpha and Beta number. For example:

occao

5 3

ROHF

Consider ROHF Fock matrix for open-shell system, or UHF Fock matrix is used.

Expert keywords

Socc

set threshold to cut small overlap between MOs and target atomic orbitals for AVAS. Default : 0.1

For example:

Socc 0.2

Depend Files

Examples

• Here, we would calculate CH2 molecule by a small basis set CC-PVDZ. Then the converged orbital will be expanded to aug-CC-PVDZ and used as the initial orbital for SCF calculation. The input file "ch2.inp" looks like

# First we perform a small basis set calculation by using CC-PVDZ.
$COMPASS
Title
 CH2 Molecule test run, cc-pvdz
Basis
 cc-pvdz
Geometry
 C     0.000000        0.00000        0.31399
 H     0.000000       -1.65723       -0.94197
 H     0.000000        1.65723       -0.94197
End geometry
UNIT
 Bohr
Check
$END

$XUANYUAN
$END

$SCF
RHF
Occupied
3  0  1  0
$END

#Change the name of check file.
%mv $BDF_WORKDIR/ch2.chkfil $BDF_WORKDIR/ch2.chkfil1
#Copy SCF converged orbital to work directory inporb.
%mv $BDF_WORKDIR/ch2.scforb $BDF_WORKDIR/ch2.inporb

# Then we init a large basis set calculation by using aug-CC-PVDZ

$COMPASS
Title
 CH2 Molecule test run, aug-cc-pvdz
Basis
 aug-cc-pvdz
Geometry
 C     0.000000        0.00000        0.31399
 H     0.000000       -1.65723       -0.94197
 H     0.000000        1.65723       -0.94197
End geometry
UNIT
 Bohr
Check
$END

# Change name of check file for large basis set.
%mv $BDF_WORKDIR/ch2.chkfil $BDF_WORKDIR/test001_1.chkfil2

# Now we expand orbital.
$expandmo
$end

# Change name of check file for large basis set.
%mv $BDF_WORKDIR/ch2.chkfil2 $BDF_WORKDIR/ch2.chkfil
# Copy expanded orbital to work directory scforb as initial guess orbital.
%mv $BDF_WORKDIR/ch2.exporb $BDF_WORKDIR/ch2.scforb

$xuanyuan
$end

# Read expanded orbital as initial guess orbital.
$scf
RHF
Occupied
 3 0 1 0
Guess
 Read
$end