##master-page:HelpTemplate ##master-date:Unknown-Date #format wiki #language en #Please change following line to BDF module name = 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 === {{{#!wiki CI effective electron Number without electrons of frozen MOs in traint module for MO integral transformation }}} Example: {{{ Electron 30 }}} === nroot === {{{#!wiki State Number, CASSCF with MixCI method needs to input state number of target CI type, which is equal to 'roots' }}} Example: === roots === {{{#!wiki State Number, CASSCF with MixCI method needs to input state number of target CI type, which is equal to 'nroot' }}} Example: === Symm === {{{#!wiki Symmetry of the target state, CASSCF with MixCI method needs to input irrep of target CI type. }}} Example: === Spin === {{{#!wiki Spin multiplicity (2S+1), CASSCF with MixCI method needs to input Spin multiplicity of target CI type. }}} === core === {{{#!wiki 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 === {{{#!wiki Number of inactive orbitals in each irreps, which is equal to 'Close' }}} Example: === Close === {{{#!wiki Number of inactive orbitals in each irreps, which is equal to 'Inactive'. }}} Example: === Active === {{{#!wiki 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. }}} === ReadDRT === {{{#!wiki read DRT from $WORKDIR/$BDFTASK.cidrt Default is .false. }}} === Nexci === {{{#!wiki set excitation number relative to reference CSFs, default = 1. }}} Example: {{{ Nexci 1 }}} === CVS === {{{#!wiki Core Valence Separation for Core excitation for GUGA if use this keyword. Default = .false. }}} Example: {{{ }}} === iCIGAS === {{{#!wiki set iCI + GAS as reference space. This keyword is equal to the simultaneous used keywords readref (or SeleREF) and GAS. Firstly automatically read REF CSF from $WORKDIR/$BDFTASK.select_*_#, where * is the spin multiplicity, # is the irreducible representation. Secondly 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: {{{ icigas 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. }}} === GAS === {{{#!wiki 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 === {{{#!wiki 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 === {{{#!wiki 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 === {{{#!wiki 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 === {{{#!wiki Maximum iteration Number of MRCISD. The default value is 500. }}} Example: {{{ Maxiter 50 }}} === ACTCRI === {{{#!wiki Set thresholds of max and min active occupation number to divide active space into RAS1, RAS2 and RAS3 for 'readref' to trancate CI space by selected reference CSFs. The active orbitals with occupation number larger than the first number are classified into RAS1, correspondingly, orbital numbers smaller than the second number are set into RAS3. Default : 2.0 and 0.0 }}} Example: {{{ Actcri 1.8 0.2 }}} === CSFCRI === {{{#!wiki Threshold of CI coefficient for reference CSFs which will read from $WORKDIR/BDFTASK.select. Default : 0.d0 }}} === PRTCRI === {{{#!wiki set threshold for CI vector print, which is equal to keyword 'CITHR'. The default value is 0.05. }}} === CITHR === {{{#!wiki set threshold for CI vector print, which is equal to keyword 'PRTCRI'. The default value is 0.05. }}} Example: {{{ CITHR 0.1 }}} === DCRI === {{{#!wiki set threshold for internal contracted CSF (ICCSF) orthonormalization. The default value is 1.d-12. }}} Example: {{{ CITHR 1.d-12 }}} === EPCC === {{{#!wiki set threshold for CI coupling coefficient which are used to form Hamiltonian matrices. The default value is 1.d-20. }}} Example: {{{ CITHR 1.d-20 }}} === Conv === {{{#!wiki 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-6 1.d-8 }}} === ETHRES === {{{#!wiki set threshold for CI energy of H0. The default value is 1.d-8 . }}} === InitHDav === {{{#!wiki 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 === {{{#!wiki 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 === {{{#!wiki 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 === {{{#!wiki 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. }}} === NCISAVE === {{{#!wiki Maximum H0 dimension can save H0 matrix, which insteads of the old keyword of 'H0TRA'. The default value is 10000. }}} === MAXREF === {{{#!wiki Maximum selected reference CSF number. The default value is 1000. }}} Example: {{{ NODE 1000 }}} === NODE === {{{#!wiki Maximum DRT node number. The default value is 100000. }}} Example: {{{ NODE 100000 }}} === WEI === {{{#!wiki Maximum DRT WEI number. The default value is 500000. }}} Example: {{{ WEI 500000 }}} === PLOOP === {{{#!wiki Maximum partial LOOP number. The default value is 500000. }}} Example: {{{ PLOOP 500000 }}} === SETICF === {{{#!wiki Maximum partial internal CSFs number in active space. The default value is 500. }}} Example: {{{ SETICF 500 }}} === SETDXY === {{{#!wiki Maximum CI subspace in active space (DXY). The default value is 50000. }}} Example: {{{ SETDXY 50000 }}} === SETH0 === {{{#!wiki Maximum reference CSF number. The default value is 500000. }}} Example: {{{ SETH0 500000 }}} === SETLOPU === {{{#!wiki Maximum Lopu number between double and active spaces. The default value is 2000. }}} Example: {{{ SETH0 500000 }}} === MAXLOOP === {{{#!wiki This keyword, alias 'Maxplp' has the function that maximum partial LOOP number for CI acceleration which is larger than or equal to keyword 'PLOOP' set value. The default value is 500000. }}} Example: {{{ MAXLOOP 500000 }}} === MAXPLP === {{{#!wiki This keyword, alias 'Maxloop' has the function that maximum partial LOOP number for CI acceleration which is larger than or equal to keyword 'PLOOP' set value. The default value is 500000. }}} Example: {{{ MAXPLP 500000 }}} === PLBLK === {{{#!wiki Maximum partial LOOP block number. The default value is 500000. }}} Example: {{{ PLBLK 500000 }}} == IC module keywords == === UCCI === {{{#!wiki This keyword is set for un-contracted MRCISD. }}} Example: {{{ UCCI }}} === VVCI === {{{#!wiki This keyword is set for contracted reference CSFs to zeroth-order wavefuctions, so that reference CSFs are not relaxed which is used together with the following contraction modes, in which reference CSFs are all relaxed by CI Hamiltonian diagonalization. The functional by this keyword is not recommended and needs testing. If use secondary states, SDSPT2 with 'dolan' or 'dylan' needs to be calculated in advance. Then the corresponding 'dolan' or 'dylan' needs to be input for icMRCI calculation. }}} Example: test069.inp {{{ VVCI }}} === FCCI === {{{#!wiki 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 === {{{#!wiki This keyword is set for one internal Contraction module of CSFs, only internal CI subspaces are not contracted. }}} Example: {{{ NICI }}} === CWCI === {{{#!wiki 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 === {{{#!wiki 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 === {{{#!wiki 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 === {{{#!wiki 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. }}} === DEPENST === {{{#!wiki Using state-dependent Fock diagonal elements in Dyall Hamiltonian, default : state-average Fock diagonal elements . }}} Example: {{{ NEVPT2 }}} === NEVPT2 === {{{#!wiki set for SS-NEVPT2 and MS-NEVPT2 calculations, where each reference state expands a specific CI space. }}} Example: {{{ NEVPT2 }}} === MR-NEVPT2 === {{{#!wiki set for SS-NEVPT2 and MS-NEVPT2 calculations, where all reference states expand only one multi-states CI space. }}} Example: {{{ MR-NEVPT2 }}} === NEVPT3 === {{{#!wiki set for SS-NEVPT3 calculation, where each reference state expands a specific CI space. }}} Example: {{{ NEVPT3 }}} === SDSPT2 === {{{#!wiki set for SDSPT2 calculation, where all reference states expand only one multi-states CI space. }}} Example: {{{ SDSPT2 }}} === SDSCI === {{{#!wiki set for SDSCI calculation, where all reference states expand only one multi-states CI space. }}} Example: {{{ SDSCI }}} === NOLAN === {{{#!wiki set for SDSPT2 and SDSCI calculations, where high-lying MCSCF wavefunction as Psi2 are used to generate Ps wavefunction in SDSPT2 and SDSCI. }}} === DOLAN === {{{#!wiki set for SDSPT2 and SDSCI calculations, where Lanczos wavefunction as Psi2 are used to generate Ps wavefunction in SDSPT2 and SDSCI. }}} === DYLAN === {{{#!wiki set for SDSPT2 and SDSCI calculations, where truncated psi(0)_i dynamically combinated Lanczos Psi2 by sum_i are used to generate Ps wavefunction in SDSPT2 and SDSCI. }}} === DEPSI2 === {{{#!wiki 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 5 eV, users can set the threshold with unit of eV. }}} === NDIMPS === {{{#!wiki 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 === {{{#!wiki set for CB-MRPT2 calculation, where each reference state expands a specific CI space. }}} Example: {{{ CBMRPT2 }}} === MR-CBMRPT2 === {{{#!wiki set for CB-MRPT2 calculations, where all reference states expand only one multi-states CI space. }}} Example: {{{ MR-CBMRPT2 }}} === MR-CBMRPT3 === {{{#!wiki 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 ++++++++++++++++++++++++++++ }}}