For MECP optimization, set MECP_OPT = TRUE in the $rem section, and note that the $derivative_coupling input section discussed in Section 9.9.2 is not necessary in this case.
MECP_OPT
MECP_OPT
Determines whether we are doing MECP optimizations.
TYPE:
LOGICAL
DEFAULT:
FALSE
OPTIONS:
TRUE
Do MECP optimization.
FALSE
Do not do MECP optimization.
RECOMMENDATION:
None.
MECP_METHODS
MECP_METHODS
Determines which method to be used.
TYPE:
STRING
DEFAULT:
BRANCHING_PLANE
OPTIONS:
BRANCHING_PLANE
Use the branching-plane updating method.
MECP_DIRECT
Use the direct method.
PENALTY_FUNCTION
Use the penalty-constrained method.
RECOMMENDATION:
The direct method is stable for small molecules or molecules with high
symmetry. The branching-plane updating method is more efficient for larger
molecules but does not work if the two states have different symmetries. If
using the branching-plane updating method, GEOM_OPT_COORDS must be
set to 0 in the $rem section, as this algorithm is available in Cartesian
coordinates only. The penalty-constrained method converges slowly and is suggested only if other methods fail.
MECP_STATE1
MECP_STATE1
Sets the first Born-Oppenheimer state for MECP optimization.
TYPE:
INTEGER/INTEGER ARRAY
DEFAULT:
None
OPTIONS:
[,]
Find the th excited state with the total spin ; means the SCF ground state.
RECOMMENDATION:
is ignored for restricted calculations; for unrestricted calculations, can only be 0 or 1.
MECP_STATE2
MECP_STATE2
Sets the second Born-Oppenheimer state for MECP optimization.
TYPE:
INTEGER/INTEGER ARRAY
DEFAULT:
None
OPTIONS:
[,]
Find the th excited state with the total spin ; means the SCF ground state.
RECOMMENDATION:
is ignored for restricted calculations; for unrestricted calculations, can only be 0 or 1.
CIS_S2_THRESH
CIS_S2_THRESH
Determines whether a state is a singlet or triplet in unrestricted calculations.
TYPE:
INTEGER
DEFAULT:
120
OPTIONS:
Sets the threshold to
RECOMMENDATION:
For the default case, states with are treated as triplet states and
other states are treated as singlets.
MECP_PROJ_HESS
MECP_PROJ_HESS
Determines whether to project out the coupling vector
from the Hessian when using branching plane updating method.
TYPE:
LOGICAL
DEFAULT:
TRUE
OPTIONS:
TRUE
FALSE
RECOMMENDATION:
Use the default.
Example 9.26 MECP optimization of an intersection between the S and S states of NO, using the direct method at the SOS-CIS(D0) level.
$molecule -1 1 N1 O2 N1 RNO O3 N1 RNO O2 AONO RNO = 1.50 AONO = 100 $end $rem JOBTYPE = opt METHOD = soscis(d0) BASIS = aug-cc-pVDZ AUX_BASIS = rimp2-aug-cc-pVDZ PURECART = 1111 CIS_N_ROOTS = 4 CIS_TRIPLETS = false CIS_SINGLETS = true MEM_STATIC = 900 MEM_TOTAL = 1950 MECP_OPT = true MECP_STATE1 = [0,2] MECP_STATE2 = [0,3] MECP_METHODS = mecp_direct $end
Example 9.27 Optimization of the ethylidene MECP between S and S at the SF-TDDFT level using the branching-plane updating method.
$molecule 0 3 C 0.044626 -0.2419240 0.357157 C 0.008905 0.6727548 1.460500 H 0.928425 -0.1459163 -0.272095 H -0.831032 -0.1926895 -0.288529 H -0.009238 0.9611331 2.479936 H 0.068314 -1.2533580 0.778847 $end $rem JOBTYPE opt METHOD bhhlyp BASIS 6-31G(d,p) MECP_OPT true MECP_METHODS branching_plane MECP_PROJ_HESS true ! project out y vector from the hessian GEOM_OPT_COORDS 0 ! currently only works for Cartesian coordinate SPIN_FLIP true UNRESTRICTED true CIS_N_ROOTS 4 MECP_STATE1 [0,1] MECP_STATE2 [0,2] CIS_S2_THRESH 120 $end
Example 9.28 Optimization of the twisted-pyramidalized ethylene MECP between S and S at the SF-TDDFT level using the penalty-constrained updating method.
$molecule 0 3 C -0.015889 0.073532 -0.059559 C 0.012427 -0.002468 1.315694 H 0.857876 0.147014 -0.710529 H -0.936470 -0.011696 -0.626761 H 0.764557 0.663381 1.762573 H 0.740773 -0.869764 1.328583 $end $rem JOBTYPE opt MECP_OPT true MECP_METHODS penalty_function METHOD bhhlyp SPIN_FLIP true UNRESTRICTED true BASIS 6-31G(d,p) CIS_N_ROOTS 4 MECP_STATE1 [0,1] MECP_STATE2 [0,2] CIS_S2_THRESH 120 $end
Example 9.29 Optimization of the and states of N at the EOM-EE-CCSD level using the direct method. See Section 7.11.27 for the specifics of performing MECP optimization with coupled cluster.
$molecule 1 1 N1 N2 N1 rNN N3 N2 rNN N1 aNNN rNN = 1.54 aNNN = 50.0 $end $rem JOBTYPE opt MECP_OPT true MECP_METHODS mecp_direct METHOD eom-ccsd BASIS 6-31g EE_SINGLETS [0,2,0,2] XOPT_STATE_1 [0,2,2] XOPT_STATE_2 [0,4,1] CCMAN2 false GEOM_OPT_TOL_GRADIENT 30 $end
Example 9.30 Optimization of the ethylidene MECP between S and S at the SF-TDDFT level with analytic derivative couplings.
$molecule 0 3 C 0.044626 -0.241924 0.357157 C 0.008905 0.672754 1.460500 H 0.928425 -0.145916 -0.272095 H -0.831032 -0.192689 -0.288529 H -0.009238 0.961133 2.479936 H 0.068314 -1.253358 0.778847 $end $rem JOBTYPE opt MECP_OPT true MECP_METHODS branching_plane MECP_PROJ_HESS true GEOM_OPT_COORDS 0 MECP_STATE1 [0,1] MECP_STATE2 [0,2] UNRESTRICTED true SPIN_FLIP true CIS_N_ROOTS 4 CALC_NAC true CIS_DER_NUMSTATE 2 SET_ITER 50 EXCHANGE bhhlyp BASIS 6-31G(d,p) integral_symmetry true $end