N-electron valence state perturbation theory (NEVPT2)

Description

Calculations using the strongly contracted state-specific n-electron valence state perturbation theory (NEVPT2) are done using the keyword "title" : "nevpt2".

Keywords

The default values are recommended unless mentioned otherwise.

frozen

Description: to have frozen orbitals or not
Datatype: bool
Default: true.

ncore

Description: manually specify number of frozen orbitals, used when ‘frozen’ is turned on with "frozen" : "true".
Datatype: int

aux_basis

Description: specify an auxiliary basis set for MP2
Datatype: string
Default: use the same density fitting basis as in Required keywords
Recommendation: use MP2-fit auxiliary basis (auxiliary basis ends with ‘ri’)

istate

Description: specific state used in the evaluation of the dynamical correlation
Datatype: int
Default: 0 (ground state)

Example

{ "bagel" : [

{
  "title" : "molecule",
  "symmetry" : "C1",
  "basis" : "svp",
  "df_basis" : "svp-jkfit",
  "angstrom" : true,
  "geometry" : [
    { "atom" : "O",  "xyz" : [ 0.00000000000, 0.0,  0.000000000000]},
    { "atom" : "H",  "xyz" : [ 1.45860189536, 0.0,  0.504283963824]},
    { "atom" : "H",  "xyz" : [ 0.75860194558, 0.0, -0.504283963824]}
  ]
},

{
  "title" : "nevpt2",
  "nact" : 2,
  "nclosed" : 4,
  "frozen" : true,
  "thresh" : 1.0e-8,
  "thresh_scf" : 1.0e-8,
  "thresh_fci" : 1.0e-10
}

]}

from which one obtains

=== DF-NEVPT2 calculation ===

     - RDMs, hole RDMs, others                   0.00
     - Fock computation                          0.01
  * 3-index integral transformation done
     - K matrices                                0.00
     - A, B, C, and D matrices                   0.00
  * ncache = 20
  * assembly done

    NEVPT2 correlation energy:   -0.1703158878      0.02

        (+0)     -0.0977514346
        (+0)'    -0.0257993320
        (+1)     -0.0086109214
        (+1)'    -0.0000000000
        (+2)     -0.0007336183
        (-1)     -0.0341475759
        (-1)'     0.0000000000
        (-2)     -0.0032730057

    NEVPT2 total energy:        -76.0205249507

References

BAGEL references

Description of Reference Reference
Relativistic implementation of NEVPT2 in BAGEL T. Shiozaki and W. Mizukami, J. Chem. Theory Comput. 11, 4733 (2015).

General references

Description of Reference Reference
Original reference for NEVPT2 C. Angeli, R. Cimiraglia, S. Evangelisti, T. Leininger, and J.-P. Malrieu, J. Chem. Phys. 114, 10252 (2001).
Spin-free formulation C. Angeli, R. Cimiraglia, and J.-P. Malrieu, J. Chem. Phys. 117, 9138 (2002).