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12.19 The ALMO-CIS and ALMO-CIS+CT Methods

12.19.2 Job Control

(December 20, 2021)

In addition to the standard CIS job controls variables described in Section 7.2.8, there are several additional $rem variables to specify for an ALMO-CIS/ALMO-CIS+CT calculation.

LOCAL_CIS

LOCAL_CIS
       Invoke ALMO-CIS/ALMO-CIS+CT.
TYPE:
       INTEGER
DEFAULT:
       0
OPTIONS:
       0 Regular CIS 1 ALMO-CIS/ALMO-CIS+CT without RI(slow) 2 ALMO-CIS/ALMO-CIS+CT with RI
RECOMMENDATION:
       2 if ALMO-CIS is desired.

NN_THRESH

NN_THRESH
       The distance cutoff for neighboring fragments (between which CT is enabled).
TYPE:
       INTEGER
DEFAULT:
       0
OPTIONS:
       0 Do not include interfragment transitions (ALMO-CIS). n Include interfragment excitations between pairs of fragments the distances between whom are smaller than n Bohr (ALMO-CIS+CT).
RECOMMENDATION:
       None

EIGSLV_METH

EIGSLV_METH
       Control the method for solving the ALMO-CIS eigen-equation
TYPE:
       INTEGER
DEFAULT:
       0
OPTIONS:
       0 Explicitly build the Hamiltonian then diagonalize (full-spectrum). 1 Use the Davidson method (currently only available for restricted cases).
RECOMMENDATION:
       None

Example 12.45  ALMO-CIS+CT calculation (rcut=10 a0) for all the n=2 states of a helium dimer.

$molecule
0 1
--
   0 1
   He      2.8    0.     0.
--
   0 1
   He      0.     0.     0.
$end

$rem
   BASIS          gen
   AUX_BASIS      rimp2-cc-pvdz
   PURECART       1111
   METHOD         hf
   SYM_IGNORE     true
   SYMMETRY       false
   FRGM_METHOD    stoll
   CIS_N_ROOTS    8
   CIS_TRIPLETS   false
   LOCAL_CIS      2 ! use RI for ALMO-CIS
   NN_THRESH      10
$end

$rem_frgm
   cis_n_roots 0
$end

$basis
****
HE   0
S    3    1.000000
3.84216340D+01    2.37660000D-02
5.77803000D+00    1.54679000D-01
1.24177400D+00    4.69630000D-01
S    1    1.000000
2.97964000D-01    1.00000000D+00
SP   1    1.000000
4.80000000D-02    1.00000000D+00   1.00000000D+00
****
$end

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