Relativistic multireference second-order perturbation theory (RelCASPT2)

Description

The relativistic version of the fully internally contracted CASPT2. As in its non-relativistic analogue, single-state calculations, multi-state calculations, and its extended variant are available. Of course, this is implemented with the automatic code generator SMITH3.

Title: relsmith

Keywords

SMITH keywords

The default values are recommended unless mentioned otherwise.

method

Description: Do multistate CASPT2.
Datatype: string
Values:
caspt2: Standard CASPT2.
casa : Use Dyall’s Hamiltonian

ms

Description: Do multistate CASPT2.
Datatype: bool
Default: true.

xms

Description: Do extended multistate CASPT2.
Datatype: bool
Default: true.

sssr

Description: Use SS-SR contraction scheme.
Datatype: bool
Default: true.

shift

Description: Vertical shift.
Datatype: double precision
Default: 0.0

thresh

Description: Convergence threshold.
Datatype: double precision
Default: For single point energy calculation, 1.0e-6. Tight convergence for gradient calculation, 1.0e-8.

thresh_overlap

Description: Overlap cutoff threshold for internally contracted basis.
Datatype: Double precision
Default: 1.0-9

frozen

Description: Freeze core orbitals.
Datatype: bool
Default: true

ncore

Description: Number of frozen core orbitals.
Datatype: int
Default: If frozen is true, subvalence orbitals are frozen. If false, zero.

nfrozenvirt

Description: Number of frozen virtual orbitals.
Datatype: int
Default: 0

block_diag_fock

Description: Using a block-diagonal zeroth-order Hamiltonian
Datatype: bool
Default: false.

maxiter

Description: Maximum number of iterations in CASPT2 calculations.
Datatype: int
Default: 50

maxtile

Description: Maximum number of orbitals in a single data tile used in CASPT2.
Datatype: int
Default: 10

cimaxtile

Description: Maximum number of Slater determinants in a single data tile used in CASPT2 gradient.
Datatype: int
Default: 100 (When number of determinants is over 10000), 10 (otherwise)
Recommendation: Use default. Increase further when the number of determinants is larger.

Example

Sample input

{ "bagel" : [

{
  "title" : "molecule",
  "basis" : "svp",
  "df_basis" : "svp-jkfit",
  "angstrom" : true,
  "geometry" : [
    { "atom" : "O",  "xyz" : [ 0.000, 0.000, 1.210 ]},
    { "atom" : "O",  "xyz" : [ 0.000, 0.000, 0.000 ]}
  ]
},

{
  "title" : "hf",
  "charge" : "+2"
},

{
  "title" : "dhf",
  "charge" : "+2"
},

{
  "title"  : "zcasscf",
  "algorithm" : "second",
  "charge" : "0",
  "state" : [0, 0, 1],
  "thresh" : 1.0e-7,
  "nclosed"  : 7,
  "nact"   : 2
},

{
  "title" : "relsmith",
  "method" : "caspt2",
  "sssr" : "false",
  "ncore" : 2,
  "ms" : "true",
  "xms" : "true",
  "shift" : "0.0"
}

]}

from which one obtains:

* Zeroth order energy : state  0       -0.4311850170
* Zeroth order energy : state  1       -0.4310720094
* Zeroth order energy : state  2       -0.4310720094

  ---- iteration ----

    0    -0.40810540     0.00007016      1.68
    1    -0.40848834     0.00000542      1.69
    2    -0.40849019     0.00000029      1.71

    0    -0.40811484     0.00007016      1.69
    1    -0.40849779     0.00000542      1.73
    2    -0.40849965     0.00000029      1.71

    0    -0.40811484     0.00007016      1.69
    1    -0.40849779     0.00000542      1.70
    2    -0.40849965     0.00000029      1.71

  -------------------


* RelCASPT2 energy : state  0     -149.9873960059
* RelCASPT2 energy : state  1     -149.9873936834
* RelCASPT2 energy : state  2     -149.9873936834

* MS-RelCASPT2 Heff
  (-149.9873960059,-0.0000000000)(-0.0000000000,0.0000000000)(0.0000000000,0.0000000000)
  (-0.0000000000,-0.0000000000)(-149.9873936834,-0.0000000000)(-0.0000000000,0.0000000000)
  (0.0000000000,-0.0000000000)(-0.0000000000,-0.0000000000)(-149.9873936834,-0.0000000000)


* MS-RelCASPT2 rotation matrix
  (1.0000000000,0.0000000000)(0.0000000000,0.0000000000)(0.0000000000,0.0000000000)
  (0.0000000000,0.0000000000)(-0.6368984967,-0.5022763292)(0.5834453739,-0.0408691780)
  (0.0000000000,0.0000000000)(-0.3871525869,-0.4383967022)(-0.8062487204,-0.0887930563)

* MS-RelCASPT2 energy : state  0     -149.9873960059
* MS-RelCASPT2 energy : state  1     -149.9873936834
* MS-RelCASPT2 energy : state  2     -149.9873936834

References

BAGEL References

Description of Reference Reference
SMITH3 M. K. MacLeod and T. Shiozaki, J. Chem. Phys. 142, 010507 (2015).
Relativistic CASPT2 T. Shiozaki and W. Mizukami, J. Chem. Theory Comput. 11, 4733 (2015).

General References

Description of Reference Reference
CASPT2 K. Andersson, P.-Å. Malmqvist, and B. O. Roos, J. Chem. Phys. 96, 1218 (1992).
MS-CASPT2 J. Finley, P.-Å. Malmqvist, B. O. Roos, and L. Serrano-Andres, Chem. Phys. Lett. 288, 299 (1998).
XMCQDPT2 A. A. Granovsky, J. Chem. Phys. 134, 214113 (2011).
XMS-CASPT2 T. Shiozaki, W. Győrffy, P. Celani, and H.-J. Werner, J. Chem. Phys. 135, 081106 (2011).