Xi'an-CI

   Xi’an-CI program generates Multi Reference SDCI (MRCISD) wavefunctions (including internal contracted MRCISD on several different level accuracy), Multi Reference Second Order Perturbation Theory (including multi-state NEVPT2 (MS-NEVPT2), Multi Reference Third Order Perturbation Theory (SS-NEVPT3), Static-Dynamic-Static Second Order Perturbation Theory (SDSPT2), Static-Dynamic-Static Configuration Interaction (SDSCI), Configuration Based Multi Reference Second Order Perturbation Theory (CB-MRPT2) and Configuration Based Multi Reference Third Order Perturbation Theory (CB-MRPT3). This program is based on hole-particle symmetry based and GUGA for the computation of CI matrix elements. The program can calculate several eigenvectors simultaneously.
   Xi’an-CI program is written by Zhenyi Wen, Yubin Wang, Zhengting Gan, Bingbing Suo and Yibo Lei (Institute of Modern Physics, Northwest University, China). 

General keywords

nroot

• State Number

Example:

Electron

• CI effective electron Number without electrons of frozen MOs in traint module for MO integral transformation

Example:

Symmetry

• Symmetry of the target state.

Example:

Spin

• Spin multiplicity. 2S+1

core

• Number of frozen orbitals in each irreps, which must be missing or set to zero in each irreps if it has frozen MOs in traint module.

Example:

Inactive

• Number of inactive orbitals in each irreps.

Example:

Active

• Number of active orbitals in each irreps.

Example:

Maxiter

• Maximum iteration Number of MRCISD.

Example:

Conv

• set threshold for CI energy, CI vector and Residual vector of MRCISD, respectively.

Example:

FCCI

• Default for internal contraction module. This keyword is set for Fully internal Contraction module of CSFs, reference CSFs are not contracted for MRCISD calculation, while perturbation theory calculation all CI subspace are internally contracted.

Example:

 FCCI

NICI

• This keyword is set for one internal Contraction module of CSFs, only internal CI subspace are not contracted.

Example:

 NICI

CWCI

• This keyword is set for one internal Contraction module of CSFs, corresponding to mrcic in molpro program for Celani-Werner (CW) contraction, where only CI subspaces VV, DV, DDV and VD in hole-particle symmetry are not contracted.

Example:

 CWCI

WKCI

• This keyword is set for one internal Contraction module of CSFs, corresponding to mrci in molpro program for Werner-Knowles (WK) contraction, where only CI subspaces with two electron excitation to external spaces are contracted.

Example:

 WKCI

SDCI

• This keyword is set for one internal Contraction module of CSFs, the accuracy of which is more accurate than CWCI but less than WKCI.

Example:

 SDCI