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2- and 4-component relativistic KR-MCSCF module ^{[1] [2] [3] [4]} original implementation written by Jørn Thyssen, Timo Fleig and Hans Jørgen Aagaard Jensen, parallelization and continuous improvement by Stefan Knecht and Hans Jørgen Aagaard Jensen. Linear symmetry adaptation by Stefan Knecht and Hans Jørgen Aagaard Jensen.

stefan: FIXME: a more detailed introduction would be most welcome.

Contents 1 Mandatory keywords 1.1 .MK2REF 1.2 .MK2DEL 1.3 .GASSH 1.4 .GASSPC 2 optional keywords under *KRMCSCF 2.1 .THRESH 2.2 .SYMMETRY 2.3 .CI PROGRAM 2.4 .INACTIVE 2.5 .MAX MACRO 2.6 .MAX MICRO 2.7 .DELETE 2.8 .SKIPEE 2.9 .SKIPEP 2.10 .PRINT 3 optional keywords under *OPTIMI 3.1 .MAX CI 3.2 .MXCIVE 3.3 .RSTRCI 3.4 .NOOCCN 3.5 .ANALYZ 4 References

Mandatory keywords

NOTE: the following keywords must be placed under the input deck

*KRMCSCF

.MK2REF

Reference value , given as (integer value); where M_K is the number of Kramers orbitals φ_p minus the number of Kramers-paired orbitals in a given determinant.

Default: None.

.MK2DEL

value of 2 * ΔM_K (integer value). The range of allowed M_K values is

Default: None.

.GASSH

Number and specification of GAS orbitals. Line with the number of GA spaces used (1-7), followed by one line per GAS with number of orbitals per fermion correp.

Default: None.

.GASSPC

specification of CI calculation. One line per GAS with 2 numbers each: The first gives the minimal number of accumulated electrons after this GAS, the second the corresponding maximum number, separated by blanks (defining occupation constraints of each GAS).

Default: None.

optional keywords under *KRMCSCF

.THRESH

convergence threshold in the MCSCF gradient given as double precision value. The present default value is quite tight and might be adapted if one is only interested in MCSCF energies.

Default:

0.5D-05

.SYMMETRY

integer value giving the (boson/fermion) symmetry of the state to optimize on.

Default:

1

If you run the calculation in linear symmetry (only available in the development version) you have to specify the 2 x OMEGA value of the state to optimize on. The doubling (2 x) stems from the fact that we want to avoid non-integer input, e.g. in case of an odd number of electrons we might have OMEGA=1/2, 3/2, 5/2, etc. values and the corresponding input for the OMEGA=1/2 would then read as

1

If we have a system with an even number of electrons and inversion symmetry the input for an OMEGA=2g state would read as

4g

.CI PROGRAM

character string reading either LUCIAREL or GASCIP. This keyword enables to choose between the two CI programs that are implemented for the MCSCF. Note that for large-scale MCSCF ( determinants) only LUCIAREL can be used.

Default:

GASCIP

.INACTIVE

Inactive orbitals per fermion correp given as integer values separated by blanks.

Default: All orbitals active.

.MAX MACRO

integer value giving the maximum number of MACRO iterations in the MCSCF optimization.

Default:

25

.MAX MICRO

integer value giving the maximum number of MICRO iterations in the MCSCF optimization.

Default:

50

.DELETE

delete particular active-secondary e-e rotations (rotations between electronic-electronic spinors) in the gradient and Hessian calculation specified by an orbital string of virtual (secondary) orbitals for each fermion correp.

Default:

include all active-secondary e-e rotations.

example: (deleting all e-e rotations for secondary orbitals 20,21 and 22 in fermion correp 1 (gerade) and 24,25,26,27 and 28 in fermion correp 2 (ungerade)):

.DELETE
20,21,22
24..28

.SKIPEE

skip e-e rotations (rotations between electronic-electronic spinors) in the gradient and Hessian calculation.

Default:

include e-e rotations.

.SKIPEP

skip e-p rotations (rotations between electronic-positronic spinors) in the gradient and Hessian calculation.

Default:

include e-p rotations.

.PRINT

raise default print level to the given integer value. Please use with care as you may get millions of output lines if you choose a too high value.

Default:

print level is 0.

optional keywords under *OPTIMI

NOTE: the following keywords must be placed under the input deck

*OPTIMI

.MAX CI

Number of initial CI iterations.

Default:

.MAX CI
 5

.MXCIVE

size of Davidson subspace.

example:

.MXCIVE
 24

Default: 3 times # of states to optimize on (remember this is a state-selective MCSCF), therefore:

3 

.RSTRCI

Optional restart from CI vector on file KRCI_CVECS.x where x is determined by the symmetry of the wave function (symmetry == 1 --> x = 1; symmetry == 2 --> x = 2; etc.). NOTE: in the DIRAC10 release version the x <==> symmetry relation is: symmetry == 1 --> x = a; symmetry == 2 --> x = b; etc.

.RSTRCI
 1

Default: No restart.

.NOOCCN

compute natural orbital occupation numbers for the electronic state.

Default:

do not compute natural orbital occupation numbers.

.ANALYZ

analyze the final CI wave function printing the coefficients for each determinant above a given threshold.

Default:

do not analyze the final CI wave function.

References

1. ↑ H. J. Aa. Jensen and K. G. Dyall and T. Saue and K. Fægri jr., Relativistic 4-component Multi-Configurational Self-Consistent Field Theory for Molecules: Formalism, J. Chem. Phys. 104, 4083 (1996) .
2. ↑ J. Thyssen, PhD thesis, University of Southern Denmark (Denmark) ', ' (2004) .
3. ↑ J. Thyssen and T. Fleig and H. J. Aa. Jensen, A Direct Relativistic Four-Component Multi-Configuration Self-Consistent-Field Method for Molecules, J. Chem. Phys. 129, 034109 (2008) .
4. ↑ S. R. Knecht, PhD thesis, University of Duesseldorf (Germany) ', ' (2009) .