*KRCI¶

.CI PROGRAM¶

specifies the CI module behind KRCI. Two choices: LUCIAREL and GASCIP

.CI PROGRAM
LUCIAREL

.CIROOTS¶

number of states (roots) in symmetry X to optimize on. This keyword may be repeated several times for multi-root multi-symmetry calculations step-by-step. default: none.

example for 5 roots in (boson/fermion) irrep 1:

.CIROOTS
1 5

If you run the calculation in linear symmetry 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 one root with the \(\Omega\) =1/2 would then read as

.CIROOTS
1 1

If we have a system with an even number of electrons and inversion symmetry the input for two \(\Omega\) =2g states read as

.CIROOTS
4g 2

.GAS SHELLS¶

Specification of CI calculation with electron distribution in orbital (GAS) spaces. The first line contains the number of GA spaces to be used (1-7), followed by one line per GAS with a separation by a “/” of the min/max number of electrons in each GAS and the number of orbitals per fermion correp (either one (no inversion symmetry) or two (inversion symmetry: gerade ungerade) entries per line).

The first entry before the “/” gives the minimal number of accumulated (!) electrons after consideration of this GAS, the second the corresponding maximum number, separated by blanks. The minimum and maximum accumulated occupations allow for a very flexible parameterization of the wave function. All determinants fulfilling the occupation constraints will be constructed. The second entry after the “/” gives the number of orbitals per fermion correp. See also the open-shell input in *SCF which is similar to the syntax used here. The design of a GAS scheme is non-trivial and should be motivated by the electronic structure of the system (e.g. inner core, outer core, valence, virtual space). Sometimes it is useful to subdivide the valence space, for scientific reasons, or/and the virtual space, for technical reasons (save core memory). See reference [Fleig2006a], pp. 27 for more details. example for 4 GAS spaces with an advanced excitation pattern:

.GAS SHELLS
 4
  1  2 /  1  0
  6  8 /  1  2
 14 16 /  7  7
 16 16 / 30 24

if all remaining orbitals (fullCI) should be included in the last GAS space, use:

.GAS SHELLS
 4
  1  2 /  1  0
  6  8 /  1  2
 14 16 /  7  7
 16 16 / all

.INACTIVE¶

Inactive orbitals per fermion correp. default: all orbitals active. example for 4 gerade and 2 ungerade orbitals frozen in a molecule with inversion center:

.INACTIVE
 4 2

.NOOCCN¶

compute natural orbital occupation numbers for each 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 \(10^{-2}\). default: do not analyze the final CI wave function.

.MAX CI¶

maximum number of CI iterations. default:

.MAX CI
 5

.MXCIVE¶

maximum size of Davidson subspace. default: 3 times the number of eigenstates (see .CIROOTS) to optimize on. example:

.MXCIVE
 24

.RSTRCI¶

Restart CI from vector(s) on file KRCI_CVECS.x where x is determined by the symmetry of the wave function.

.RSTRCI
 1

default: no restart.

.RSTRCI
 0

further infomation: the convention in linear symmetry for KRCI_CVECS.x is the following where the offset/range for systems with a gerade number of electrons is for x: offset –> 1; range: x =[1-64] and with an ungerade number of electrons x: offset –> 65; range: x =[65-128]. In more detail (with MJ == \(\Omega\)):

1. for systems with a gerade number of e- and no inversion center:

MJ =  0: KRCI_CVECS.1
MJ = +1: KRCI_CVECS.2
MJ = -1: KRCI_CVECS.3
MJ = +2: KRCI_CVECS.4
MJ = -2: KRCI_CVECS.5
...
up to
MJ = +32: KRCI_CVECS.64

2. for systems with a gerade number of e- and an inversion center:

MJ =  0g: KRCI_CVECS.1
MJ = +1g: KRCI_CVECS.2
MJ = -1g: KRCI_CVECS.3
MJ = +2g: KRCI_CVECS.4
MJ = -2g: KRCI_CVECS.5
...
up to
MJ = +16g: KRCI_CVECS.32

and
MJ =  0u: KRCI_CVECS.33
MJ = +1u: KRCI_CVECS.34
MJ = -1u: KRCI_CVECS.35
MJ = +2u: KRCI_CVECS.36
MJ = -2u: KRCI_CVECS.37
...
up to
MJ = +16u: KRCI_CVECS.64

3. for systems with an ungerade number of e- and no inversion center:

MJ = +1/2: KRCI_CVECS.65
MJ = -1/2: KRCI_CVECS.66
MJ = +3/2: KRCI_CVECS.67
MJ = -3/2: KRCI_CVECS.68
...
up to
MJ = +63/2: KRCI_CVECS.128

4. for systems with an ungerade number of e- and an inversion center:

MJ = +1/2g: KRCI_CVECS.65
MJ = -1/2g: KRCI_CVECS.66
MJ = +3/2g: KRCI_CVECS.67
MJ = -3/2g: KRCI_CVECS.68
...
up to
MJ = -31/2g: KRCI_CVECS.96

and

MJ = +1/2u: KRCI_CVECS.97
MJ = -1/2u: KRCI_CVECS.98
MJ = +3/2u: KRCI_CVECS.99
MJ = -3/2u: KRCI_CVECS.100
...
up to
MJ = -31/u: KRCI_CVECS.128

.CHECKP¶

enables a check point write of the current solution vectors to the file KRCI_CVECS.x (see above in .CIROOTS for an explanation of how x is supposed to be replaced) during the Davidson iterations. A checkpoint file will be written roughly every 6th iteration. default: do not write check points.

.IJKLRO¶

enables the storage of the resorted two-electron integrals on file IJKL_REOD which can then be read-in in a restart. This avoids a multiple reading from the 4IND* files and subsequent resorting. The keyword has to be present also in the restart to enable the potential read-in procedure. Hint: This keyword may be combined with .MAX CI == 0 in a precedent step in order to save memory for the actual production run. This is due to the fact that the resorting step itself requires the in-core storage of the unsorted and sorted integrals. default: do not write the resorted integrals to file IJKL_REOD.

.IJKLSP¶

enables the splitting of the resorted integrals among the co-workers according to their needs in the computation of the sigma vector. It can only be used in combination with .IJKLRO. default: do no split the resorted integrals among the co-workers.

.DIPMOM¶

compute the permanent dipole moments in electronic ground and excited states.

.TRDM¶

compute the transition dipole moments between electronic states.

.OMEGAQ¶

Note: this keyword may only be used for linear molecules.

compute the expectation values of the spin- and angular momentum operator in z-direction and print the total \(\hat{j}_z\) = \(\hat{s}_z\) + \(\hat{l}_z\) expectation value (\(\Omega\) value) for each electronic state.