Xi'an-CI Program

   Xi’an-CI program generates Multi Reference SDCI (MRCISD) wavefunctions (including internal contracted MRCISD on several different level accuracy), N-electron Valence states Second Order Perturbation Theory (including multi-state NEVPT2 (MS-NEVPT2), N-electron Valence states Third Order Perturbation Theory (NEVPT3), Static-Dynamic-Static Second Order Perturbation Theory (SDSPT2), Static-Dynamic-Static Configuration Interaction (SDSCI), Configuration Based Multi Reference Second Order Perturbation Theory (CBMRPT2) and Configuration Based Multi Reference Third Order Perturbation Theory (CBMRPT3). This program is based on hole-particle symmetry 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). 

Corresponding email

bsuo@nwu.edu.cn (Prof. Bingbing Suo) 
leiyb@nwu.edu.cn (Prof. Yibo Lei) 
wzy@nwu.edu.cn (Prof. Zhenyi Wen)
yubin_wang@hotmail.com (Prof. Yubin Wang)

References

Xi’an-CI Program Package Review 
1.      B. Suo, Y. Lei, H. Han, Y. Wang, Mol. Phys., 116, 1051 (2018).

ucMRCISD program
1.      Y. Wang, G. Zhai, B. Suo, Z. Gan, Z. Wen, Chem. Phys. Lett., 375, 134 (2003).
2.      Y. Wang, Z. Wen, Z. Zhang, Q. Du, J. Comput. Chem, 13, 187 (1992).
3.      Y. Lei, B. Suo, Y. Dou, Y. Wang, Z. Wen,  J. Comput. Chem, 31, 1752 (2010).
4.      B. Suo, G. Zhai, Y. Wang, Z. Wen, X. Hu, L. Li, J. Comput. Chem, 26, 88 (2005).  
5.      Z. Gan, K. Su, Y. Wang, Z. Wen, Sci. China Ser. B-Chem, 42, 43 (1999).
6.      Z. Wen, Y. Wang, H. Lin, Chem. Phys. Lett., 230, 41 (1994).

icMRCISD program
1.      Y. Wang, H. Han, Y. Lei, B. Suo, H. Zhu, Q. Song, Z. Wen, J. Chem. Phys., 141, 164114 (2014).
2.      B. Suo, Y. Lei, H. Han, Y. Wang, Mol. Phys., 116, 1051 (2018).

MS-NEVPT2 program
1.      C. Angeli, R. Cimiraglia, S. Evangelisti, T. Leininger, J.P.Malrieu, J. Chem. Phys., 114, 10252 (2001).
2.      Y. Lei, W. Liu, M. R. Hoffmann, Mol. Phys., 115, 2696 (2017).
3.      B. Suo, Y. Lei, H. Han, Y. Wang, Mol. Phys., 116, 1051 (2018).

SDSPT2 program
1.      Y. Lei, W. Liu, M. R. Hoffmann, Mol. Phys., 115, 2696 (2017).
2.      W. Liu, M.R. Hoffmann, Theor. Chem. Acc., 133, 1481 (2014).
3.      W. Liu, M.R. Hoffmann, J. Chem. Theory Comput., 12, 1169 (2016); 12, 3000(E) (2016).

CBMRPT2 program
1.      Y. Lei, Y. Wang, H. Han, Q. Song, B. Suo, Z. Wen, J. Chem. Phys., 137, 144102 (2012).
2.      A. Li, H. Han, B. Suo, Y. Wang, Z. Wen, Sci. China CHEMISTRY, 53. 933 (2010).
3.      Y. Wang, Z. Gan, K. Suo, Z, Wen, Sci. China Ser. B-Chem, 43, 567 (2000).

General keywords

Comment:

   If no keyword is used, xianci module will read information from mcscf and traint modules and then calculate Fully internal contracted MRCISD. 

Electron

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

Example:

Electron
 30

nroot

• State Number, CASSCF with MixCI method needs to input state number of target CI type, which is equal to 'roots'

Example:

roots

• State Number, CASSCF with MixCI method needs to input state number of target CI type, which is equal to 'nroot'

Example:

istate

• Set the selected root index with total root number set firstly. The keyword supports only NEVPT2, SDSPT2, SDSCI and eSDSCI.

Example:

istate
2    ！the total number of the selected roots
1 3  ! select the first and third roots.

Symm

• Symmetry of the target state, CASSCF with MixCI method needs to input irrep of target CI type.

Example:

Spin

• Spin multiplicity (2S+1), CASSCF with MixCI method needs to input Spin multiplicity of target CI type.

core

• Number of frozen or doubly occupied orbitals in each irreps. Default : no frozen orbitals.

Example:

Dele

• Number of deleted virtual orbitals in each irreps. Default : no deleted orbitals.

Example:

ORBTXT

set to read BDF_WorkDir text orbital file, such as $BDF_WORKDIR/$BDFTASK.inporb

Example:

Orbtxt
inporb

XvrUse

The keyword for alternatively deleting virtual MOs by MCSCF XVR when keyword 'Dele' are not used to set delete MOs. Default is .false. However, the keyword 'Dele' is prior to 'XvrUse'.

QNEX

We defaultly approximately construct \bar{V}D and \bar{D}V subspaces by N^{{ex} {\bar{V}D}=1 and N}{ex}_{\bar{D}V}=1. As this keyword is used N^{{ex}_{\bar{V}D}=2 and N}{ex}_{\bar{D}V}=2.

Inactive

• Number of inactive orbitals in each irreps, which is equal to 'Close'

Example:

Close

• Number of inactive orbitals in each irreps, which is equal to 'Inactive'.

Example:

Active

• Number of active orbitals in each irreps.

Example:

Comment:

  If the above keywords are not set. the mcscf and traint modules information will be used. 

SubDRT

• active the function to parallel form sub-DRT. Default .TRUE.

Example:

Comment:

  If the above keywords are not set. the mcscf and traint modules information will be used. 

XSDSCI

• Calculate MRPT2 and MRCISD by SS-NEVPT2, MS-NEVPT2, SDSPT2+Q, SDSCI+Q and icMRCISD+Q. For icMRCISD, use MCSCF reference function and first-order wave function from purbutation theory as initial trial vectors to accelerate Davidson diagnoalization, deault : .false. This

keyword has the same funtion as the old keyword of eSDSCI.

Example:

 XSDSCI

VSD

Use Virtual Space Decompostion (VSD) formed MOs to calculate XSDSCI, so that this keyword is combined with XSDSCI. VSD is used to separate Virtual MOs of large basis set by the selection of N(L)-N_occ of nonzero SVD value of <Psi(vir)|Phi(projected small basis set)>. This divide Virtual space into strong correlated space and weak correlated space, respectively.

Example: test126.inp

Notice : The number of virtual MOs by large basis set must be larger than the number of small basis set.

NoVDVP

Skip calculation of \bar(V)D and \bar(V)P for MRPT2.

Example: test148.inp

Notice : The number of virtual MOs by large basis set must be larger than the number of small basis set.

MRCI

• Calculate MRCISD where the reference CSFs are default optimized with the assistance of internal contraction mode. Deault : .true.

Example:

 MRCI

Qss

• Use state-specific Q space for NEVPT2, SDSPT2 and SDSCI, default : .true.

Qms

• Use state-universal Q space for NEVPT2, SDSPT2 and SDSCI, default : .false.

H0Fock

• Use generalized Fock operator as zeroth-order Hamiltonian (H0) to calculate <Q|H0|Q>, which is remarkably quicker than that use Dyall Hamiltonian as H0. Default : .false.

H0Dyall

• Use Dyall Hamiltonian as zeroth-order Hamiltonian (H0) to calculate <Q|H0|Q>, which is remarkably slower than that use generalized Fock operator as H0. Default : .true.

SAFOCK

• Use state-average CMO energies and integrals for NEVPT2, SDSPT2 and SDSCI, default : .true.

SSFOCK

• Use state-dependent CMO energies and integrals for NEVPT2, SDSPT2 and SDSCI, default : .false.

SDFOCK

• Use state-dependent CMO energies and state-average CMO integrals for NEVPT2, SDSPT2 and SDSCI, default : .false.

CSFiCI

• This keyword can set to use reference CSF but not oCFG. If keyword 'CFGiCI' on MCSCF or Xianci module is set, this functional does not work. When 'CSFiCI' on Xianci module is set, it works. When it is active, users can use iCISCF with respect to reference CSF.

CFGiCI

• This keyword can set to use reference oCFG but not CSF. Default : .false. If keyword 'CFGiCI' on MCSCF or Xianci module is set, this functional works. When it is active, users can use iCISCF with respect to reference oCFG which can be used by keyword CFGiCI on MCSCF.

Cmin

• Threshold of CI coefficient for reference CSFs when use keyword 'CSFiCI', the Cmin value can be read from MCSCF for iCISCF(2), or users can set this keyword manually. Cmin can be used to select reference CSF but not oCFG after the pre-calculation of H0 diagonalization with respect to reference oCFG.

Pmin

• Threshold of CI coefficient for reference CSFs which will read from $WORKDIR/$BDFTASK.select_*_#, where * is the spin multiplicity, # is the irreducible representation. Default : 0.0. The input threshold should be larger than the default 0.0. When use this keyword the P space will be enlarged and E(H0) will use the enlarged P space energy and iCIPT2 energy will be set to zero.

When do not use this keyword the E(H0) energy is equal to iCISCF energy and iCIPT2 energy will be added to the following MRCISD or MRPT2. This keyword is equal to 'CSFCRI'.

Qmin

• Threshold of uniquely pruning Q subspaces to reduce internally contracted wavefunctions (it|uv),(tu|va),(iu|va), (ij|uv) and (uv|ab) by semistochastic heat-bath CI (SBCI) with max<q|H|0> < Qmin, default : 0.d0.

QminDV

• Threshold of internal contraction coefficient to reduce \bar(D)V internally contracted wavefunctions (it|uv) by semistochastic heat-bath CI (SBCI) with max<q|H|0> < QminDV, default : 0.d0.

QminVD

• Threshold of internal contraction coefficient to reduce \bar(V)D internally contracted wavefunctions (tu|va) by semistochastic heat-bath CI (SBCI) with max<q|H|0> < QminVD, default : 0.d0.

QminDD

• Threshold of internal contraction coefficient to reduce \bar(D)D internally contracted wavefunctions (iu|va) by semistochastic heat-bath CI (SBCI) with max<q|H|0> < QminDD, default : 0.d0.

QminPV

• Threshold of internal contraction coefficient to reduce \bar(P)V internally contracted wavefunctions (ij|uv) by semistochastic heat-bath CI (SBCI) with max<q|H|0> < QminPV, default : 0.d0.

QminVP

• Threshold of internal contraction coefficient to reduce \bar(V)P internally contracted wavefunctions (uv|ab) by semistochastic heat-bath CI (SBCI) with max<q|H|0> < QminVP, default : 0.d0.

Qfix

• Threshold to Fix CI coefficients of Q space for ic-MRCISD diagonalization, default : 0.d0.

ICreduce

• This keyword is used to reduce \bar(D)V and \bar(V)D internally contracted wavefunctions by merging direct and exchanged ploops, so that the pair two IC functions with the small active orbital indexes are merged together. Default : .true.

NoICredu

• This keyword is used to do not reduce \bar(D)V and \bar(V)D internally contracted wavefunctions by merging direct and exchanged ploops, so that the pair two IC functions with the small active orbital indexes are merged together. Default : .false.

ReadDRT

• read DRT from $WORKDIR/$BDFTASK.cidrt Default is .false.

Nexci

• set excitation number relative to reference CSFs, default = 2 for MRCISD/MRPT2. If Nexci=1 for MRCIS or MRPT2 with only one electron excitation.

Example:

Nexci

1

CVS

Core Valence Separation for Core excitation for GUGA if use this keyword. Default = .false.

Example:

GAS

several lines should be provided for controlling GASSCF calculations. Default is read from MCSCF and needs not to set. Line 1: number for GAS spaces, like GAS1, GAS2, GAS3, .... Line 2: minimum electron occupation numbers for the GAS spaces. Line 3: maximum electron occupation numbers for the GAS spaces. From Line 4 to Line (GAS spaces number plus 3) set active orbital with symmetry of these GAS spaces.

Example:

gas
2    ! there are two GAS spaces.
2 4  ! minimum electron occupation numbers for the GAS spaces.
4 10 ! maximum electron occupation numbers for the GAS spaces.
2 0 0 0  ! active orbitals of each irreps of GAS1
2 0 2 2  ! active orbitals of each irreps of GAS2.

Comment:

   With keyword 'GAS' setting, keywords 'active' is useless and can be missing.

ReadREF

• Automatically read REF CSF from $WORKDIR/$BDFTASK.select_*_#, where * is the spin multiplicity, # is the irreducible representation. The functional is combined with keyword 'CSFCRI' to read and select reference CSF from text file.

Example:

$xianci
...
READREF
...
$end 

SeleREF

• Line 1: Set Number of Selected CSF occupations (Nref). Line 2 to Line Nref+1: set occupation (2,1,0) respectively to double, single and zero occupation.

Example:

SELEREF 
 3 
2200  
2110  
2020  

RootPrt

• Print the target state (root) energy for calculating numerical gradient of this state in numgrad module, default is 1.

Example:

RootPrt
 3   # the third state (root) energies will be printed. 

Maxiter

• Maximum iteration Number of Davidson Diagonalization used in Xi'an-CI. The default value is 200.

Example:

Maxiter
 50

PRTCRI

• set threshold for CI vector print, which is equal to keyword 'CITHR'. The default value is 0.05.

CITHR

• set threshold for CI vector print, which is equal to keyword 'PRTCRI'. The default value is 0.05.

Example:

CITHR 
 0.1

RShift

• set real level shift for <Q|H(0)-E(0)+Rshift|Q>. The default value is 0.d0. Recommend: 0.3

Example:

Rshift
0.3

VDRLS

• set real level shift for <\bar{V}D|H(0)-E(0)+VDRLS |\bar{V}D>. The default value is 0.d0. Recommend: 0.3

Example:

VDRLS
0.3

DVRLS

• set real level shift for <\bar{D}V|H(0)-E(0)+DVRLS |\bar{D}V>. The default value is 0.d0. Recommend: 0.3

Example:

DVRLS
0.3

DDRLS

• set real level shift for <\bar{D}D|H(0)-E(0)+DDRLS |\bar{D}D>. The default value is 0.d0. Recommend: 0.3

Example:

DDRLS
0.3

IShift

• set imaginary level shift for <Q|H(0)-E(0)+Ishift|Q>. The default value is 0.d0. Recommend: 0.3

Example:

Ishift
0.3

VDILS

• set imaginary level shift for <\bar{V}D|H(0)-E(0)+VDILS |\bar{V}D>. The default value is 0.d0. Recommend: 0.3

Example:

VDILS
0.3

DVILS

• set imaginary level shift for <\bar{D}V|H(0)-E(0)+DVILS |\bar{D}V>. The default value is 0.d0. Recommend: 0.3

Example:

DVILS
0.3

DDILS

• set imaginary level shift for <\bar{D}D|H(0)-E(0)+DDILS |\bar{D}D>. The default value is 0.d0. Recommend: 0.3

Example:

DDILS
0.3

DCRI

• set threshold for internal contracted CSF (ICCSF) deleting and linear-dependent orthonormalization. The default value is 1.d-12.

Example:

CITHR 
 1.d-12

EPIC

• set threshold for internal contracted coefficient which are used to form Hamiltonian matrices. The default value is 0.d0. Recommend: 1.d-5

Example:

epic
1.d-5

EPCC

• set threshold for CI coupling coefficient which are used to form Hamiltonian matrices. The default value is 0.d0. Recommend: 1.d-10

Example:

epcc
1.d-10

Conv

• set threshold for CI energy, CI vector and Residual vector of MRCISD, respectively. The default value is set as the following example.

Example:

Conv
1.d-8 1.d-4 1.d-8

ETHRES

• set threshold for CI energy of H0. The default value is 1.d-8 .

InitHDav

• Set 1 for initial vectors on Davidson diagonalization by largest coupling with energy lowest CSFs，which is default. Set 2 for initial vectors on Davidson diagonalization by low-lying CI Hamiltonian diagonal elements near by reference states. Set 3 for initial vectors on Davidson diagonalization by the residual vector of reference wavefunctions.

InitH0Dav

• Set 1 for initial vectors of P space on Davidson diagonalization by largest coupling with energy lowest CSFs for the H0 diagonalization. Set 2 for initial vectors of P space on Davidson diagonalization by low-lying CI Hamiltonian diagonal elements near by reference CSFs for the H0 diagonalization, which is default.

FollowDav

• If this keyword is specified in a MRCISD calculation, and if the $numgrad block is present, the numerical gradient calculation will use the MRCISD+Q energies. Otherwise the uncorrected MRCISD energies will be used.

Memory keywords

Nosavelp

• set to calculate partial loops on each MRCI iteration individually. This leads to more MRCI calculation time but saves hard disk and should be used to the system with large active space.

H0Tra

• Maximum H0 dimension can completely diagonalize H0 matrix. The default value is 1000.

NCISAVE

• Maximum H0 dimension can save H0 matrix, which insteads of the old keyword of 'H0TRA'. The default value is 50000.

MAXREF

• Maximum selected reference CSF number. The default value is 50000.

Example:

NODE 
 50000

NODE

• Maximum DRT node number. The default value is 1000000.

Example:

NODE 
 1000000

subNODE

• Maximum sub-DRT node number. The default value is 1000000.

Example:

NODE 
 100000

Maxload

• Set largest number of IC coefficient of each block. Default: 10000000000.

PLBLK

• Maximum partial LOOP block number. The default value is 2000000.

Example:

PLBLK
 10000000

IC module keywords

UCCI

• This keyword is set for un-contracted MRCISD.

Example:

 UCCI

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 subspaces are internally contracted.

Example:

 FCCI

NICI

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

Example:

 NICI

CWCI

• This keyword is set for one internal Contraction module of CSFs, corresponding to keyword '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 keyword '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. In contrast with WKCI module, CI subspaces with two electron excitation from hole space and meanwhile one electron excitation to external space are also contracted.

Example:

 SDCI

XDCI

• This keyword is set for one internal Contraction module of CSFs, where XS(T), S(T)V and S(T)D are not contracted.

Example:

 XDCI

MRPT keywords

Comment:

  If no keyword is set for perturbation theory calculation in the following, xianci module will calculate MRCISD in default. 

Notice:

  The following methods use Fully internal contraction wavefunction (FCCI) as default, while NICI, CWCI, SDCI, WKCI modules should be set in turn for the case FCCI module fails.  

NEVPT2

• set for SS-NEVPT2 and MS-NEVPT2 calculations, where each reference state expands a specific CI space.

Example:

 NEVPT2

MR-NEVPT2

• set for SS-NEVPT2 and MS-NEVPT2 calculations, where all reference states expand only one multi-states CI space.

Example:

 MR-NEVPT2

NEVPT3

• set for SS-NEVPT3 calculation, where each reference state expands a specific CI space.

Example:

 NEVPT3

SDSPT2

• set for SDSPT2 calculation, where all reference states expand only one multi-states CI space.

Example:

 SDSPT2

SDSCI

• set for SDSCI calculation, where all reference states expand only one multi-states CI space.

Example:

 SDSCI

DYLAN

• set for SDSPT2 and SDSCI calculations, where truncated psi(0)_i dynamically combinated Lanczos Psi2 by sum_i<psi(0)_i|H|Psi(1)> are used to generate Ps wavefunction in SDSPT2 and SDSCI. Default = .true.

NOLAN

• set for SDSPT2 and SDSCI calculations, where high-lying MCSCF wavefunction as Psi2 are used to generate Ps wavefunction in SDSPT2 and SDSCI. Default = .false.

DOLAN

• set for SDSPT2 and SDSCI calculations, where Lanczos wavefunction as Psi2 are used to generate Ps wavefunction in SDSPT2 and SDSCI. Default = .false.

DEPSI2

• set threshold for the cutoff of the calculated number of H0 states, those of which are high-lying than the target states. The default value is 0.5 eV, users can set the threshold with unit of eV.

NDIMPS

• set for SDSPT2 and SDSCI calculations, where CASSCF wavefunctions are used to produce Ps wavefunction in SDSPT2 and SDSCI.

Example:

 NDIMPS
  2   # two high-lying CASSCF wavefunctions are used to produce Ps wavefunction in SDSPT2 and SDSCI relative to reference wavefunctions.

Comment:

 If Keyword 'NDIMPS' are not set or set to zero and keyword 'NOLAN' are set, SDSPT2 or SDSCI has no Ps wavefunction. 

CBMRPT2

• set for CB-MRPT2 calculation, where each reference state expands a specific CI space.

Example:

 CBMRPT2

MR-CBMRPT2

• set for CB-MRPT2 calculations, where all reference states expand only one multi-states CI space.

Example:

 MR-CBMRPT2 

MR-CBMRPT3

• set for CB-MRPT3 calculations, where all reference states expand only one multi-states CI space.

Example:

 MR-CBMRPT3 

Examples

Test Example 1

input:

$COMPASS 
Title
 C2H4 Molecule test run
Basis
 cc-pvdz
Geometry
 C             0.000000       1.386400       0.000000    
 C             0.000000      -1.386400       0.000000    
 C             2.099700       2.794200       0.000000    
 C            -2.099700      -2.794200       0.000000    
 H            -1.845200       2.307000       0.000000    
 H             1.845200      -2.307000       0.000000    
 H             3.968500       1.930200       0.000000    
 H            -3.968500      -1.930200       0.000000    
 H             2.015100       4.847500       0.000000    
 H            -2.015100      -4.847500       0.000000    
END geometry
Check
unit
bohr
$END

$xuanyuan
$end

$SCF
RHF
charge
 0
spin
 1
$END

$MCSCF
close
 7   0   0   5
active
 0   2   3   1
actele
 6
spin
 1
symmetry
 1
roots
 3 3 
 1 2 3 
 1 1 1 
mixci
 2  
 1 3
 2 1
 1 4 
ROOTPRT
 1
prtcri
0.1
guess
hforb
$END

$TRAINT
Frozen
 2 0 0 2 0 0 0 0 
Orbital
 mcorb
$END

$XIANCI
nroot
2
spin
1
symmetry
1
$END

$XIANCI
nroot
1
spin
3
symmetry
4
$END

Results:

========================= mcscf results ==============================
    State Averaged ci energy      -154.86258790

    root   1
    energy=     -154.98691206     exe(eV)=    0.0000


    root   2
    energy=     -154.73707954     exe(eV)=    6.7983


    root   3
    energy=     -154.86377210     exe(eV)=    3.3508

 
 ++++++++  DATA CHECK +++++++++++++++++++++++++++++++++
  CHECKDATA:MCSCF:MCENERGY:     -154.9869121     -154.7370795     -154.8637721
 ++++++++++ END DATA CHECK ++++++++++++++++++++++++++++
 
  End   MCSCF Calculation

========================= xianci results ==============================

=============================== For first type of CI with two singlet states ====================================

 Roots of Heff are calculated are listed below: 
 
                        ENE           ENE + Pople       ENE + App Pople       ENE + DAV           ENE + MEISS
  root   1       -155.45209027       -155.52854668       -155.52960628       -155.51383149       -155.51395190
  root   2       -155.19957647       -155.27731997       -155.27842584       -155.26200965       -155.26229526
               MRCISD energyies     Pople Correction  App Pople Correction  Davidson Correction  Meissner correction    

 =====================================================

 MRSDCI CALCULATION CONVERGED

 NROOT      MC ENERGY        CI ENERGY          CI DAV             DAVCOEF
   1     -154.98691206    -155.45209027      -155.51383149         0.867274
   2     -154.73707954    -155.19957647      -155.26200965         0.865008
         MCSCF energyies  MRCISD energyies Davidson Correction  Reference weight   
    
    root   1
    energy=     -155.45209027     exe(eV)=    0.0000


    root   2
    energy=     -155.19957647     exe(eV)=    6.8713

 
 ++++++++  DATA CHECK +++++++++++++++++++++++++++++++++
  CHECKDATA:MRCI:CIENERGY:     -155.4520903     -155.1995765
 ++++++++++ END DATA CHECK ++++++++++++++++++++++++++++

=============================== For second type of CI with one triplet state ====================================
 

 Roots of Heff are calculated are listed below: 
 
                        ENE           ENE + Pople       ENE + App Pople       ENE + DAV           ENE + MEISS
  root   1       -155.32503309       -155.40089070       -155.40194273       -155.38628185       -155.38640551
 
 =====================================================

 MRSDCI CALCULATION CONVERGED

 NROOT      MC ENERGY        CI ENERGY        CI DAV         DAVCOEF
   1     -154.86377210    -155.32503309    -155.38628185    0.867215

    root   1
    energy=     -155.32503309     exe(eV)=    0.0000

 
 ++++++++  DATA CHECK +++++++++++++++++++++++++++++++++
  CHECKDATA:MRCI:CIENERGY:     -155.3250331
 ++++++++++ END DATA CHECK ++++++++++++++++++++++++++++

Test Example 2

input:

$TRAINT
Frozen
 2 0 0 2 0 0 0 0 
Orbital
 mcorb
mrpt2
$END

$XIANCI
nroot
2
spin
1
symmetry
1
SDSPT2
$END

Results:

=============================== For first type of CI with two singlet states ====================================

 NROOT   MC ENE        SS-NEVPT2 ENE   MS-NEVPT2 ENE     SDSPT2 ENE    SDSPT2+Q1 ENE   SDSPT2+Q2 ENE        SDSPT2+Q3 ENE       DAVCOEF
   1   -154.98691206   -155.47745410   -155.47745446   -155.41455599   -155.47503759   -155.47574313       -155.46512580        0.881748
   2   -154.73707954   -155.21961390   -155.21961354   -155.15793413   -155.21775988   -155.21846183       -155.20789974        0.881276
Energies:   MCSCF       SS-NEVPT2       MS-NEVPT2         SDSPT2    Pople Correction App Pople Correction Davidson Correction Ref. Weight 

Test Example 3

input:

$XIANCI
nroot
2
spin
1
symmetry
1
SDSCI
$END

Results:

=============================== For first type of CI with two singlet states ====================================

 NROOT   MC ENE        SS-NEVPT2 ENE   MS-NEVPT2 ENE     SDSPT2 ENE    SDSPT2+Q1 ENE   SDSPT2+Q2 ENE   SDSPT2+Q3 ENE   DAVCOEF
   1   -154.98691206   -155.47745410   -155.47745446   -155.44006672   -155.51313986   -155.51413050   -155.49935009   0.869176
   2   -154.73707954   -155.21961390   -155.21961354   -155.18843582   -155.26361048   -155.26466844   -155.24894428   0.865941
Energies:   MCSCF       SS-NEVPT2       MS-NEVPT2         SDSCI  Pople Correction App Pople Correction Davidson Correction Ref. Weight 

Test Example 4

input:

$XIANCI
nroot
2
spin
1
symmetry
1
NEVPT3
$END

Results:

=============================== For first type of CI with two singlet states ====================================

 NROOT        MC ENERGY       SS-NEVPT2 ENERGY    MS-NEVPT2 ENERGY    SS-NEVPT3 ENERGY    MS-NEVPT3 ENERGY
   1       -154.98691206       -155.47742562       -155.47742574       -155.51364676       -155.51364676
   2       -154.73707954       -155.21952164       -155.21952152       -155.26247430       -155.26247430
Energies:     MCSCF             SS-NEVPT2            MS-NEVPT2          SS-NEVPT3            Useless

Test Example 5

input:

$XIANCI
nroot
2
spin
1
symmetry
1
CBMRPT2
$END

Results:

=============================== For first type of CI with two singlet states ====================================

 ++++++++  DATA CHECK +++++++++++++++++++++++++++++++++
  CHECKDATA:MRPT2:PT2ENERGY:     -155.5496768     -155.2931467
 ++++++++++ END DATA CHECK ++++++++++++++++++++++++++++

Test Example 6

input:

$XIANCI
nroot
2
spin
1
symmetry
1
MR-CBMRPT3
$END

Results:

=============================== For first type of CI with two singlet states ====================================

 ++++++++  DATA CHECK +++++++++++++++++++++++++++++++++
  CHECKDATA:MRPT3:PT3ENERGY:     -155.5176000     -155.2629435
 ++++++++++ END DATA CHECK ++++++++++++++++++++++++++++