ASD-DMRG

Description

ASD-DMRG algorithm is able to deal with molecular aggregates with more than two sites.

Multisite construction

Keywords

method

Description: Method to compute active subspaces.
Datatype: string
Value:
ras: use restricted active space configuration interaction method

ras

Description: Specify restricted active space method settings.

restricted

Description: Specify occupation restriction in active space.
Recommendation: See sample input for details.

spaces

Description: Specify important single site states with the following keys:
charge, spin, nstate
Recommendation: See sample input for details.

nstates

Description: Number of target states.
Datatype: int
Default 1

ntrunc

Description: Number of dmrg states to keep.
Datatype: int

thresh

Description: Threshold for convergence in Davidson diagonalization.
Datatype: double

maxiter

Description: Maximum number of iterations for Davidson diagonalization.
Datatype: int
Default: 50

perturb

Description: Initial perturbation value.
Datatype: double
Default: 0.001
Recommendation: Use default.

perturb_thresh

Description: Threshold for energy convergence when perturbation is applied.
Datatype: double
Default: 0.0001
Recommendation: Use default.

perturb_min

Description: Minimum perturbation to be applied.
Datatype: double
Default: 0.00001
Recommendation: Use default.

Example

Here is a sample calculation of Helium trimer aggregate with ASD-DMRG.

Sample input

{ "bagel" : [

{
  "title" : "molecule",
  "basis" : "svp",
  "df_basis" : "svp-jkfit",
  "angstrom" : false,
  "cartesian" : false,
  "geometry" : [
    {"atom" :"He", "xyz" : [    0.00000000000,     0.00000000000,     0.00000000000] }
  ]
},

{
  "title" : "hf",
  "saveref" : "A"
},

{
  "title" : "molecule",
  "basis" : "svp",
  "df_basis" : "svp-jkfit",
  "angstrom" : false,
  "cartesian" : false,
  "geometry" : [
    {"atom" :"He", "xyz" : [    0.00000000000,     0.00000000000,     3.00000000000] }
  ]
},

{
  "title" : "hf",
  "saveref" : "B"
},

{
  "title" : "molecule",
  "basis" : "svp",
  "df_basis" : "svp-jkfit",
  "angstrom" : false,
  "cartesian" : false,
  "geometry" : [
    {"atom" :"He", "xyz" : [    0.00000000000,     0.00000000000,     6.00000000000] }
  ]
},

{
  "title" : "hf",
  "saveref" : "C"
},

{
  "title" : "multisite",
  "refs" : ["A", "B", "C"],
  "active" : [ [1, 2, 3, 4, 5] ],
  "hf" : {
    "thresh" : 1.0e-12
  },
  "localization" : {
    "max_iter" : 50,
    "thresh" : 1.0e-12
  }
},

{
  "title" : "asd_dmrg",
  "nstate" : 2,
  "ntrunc" : 100,
  "method" : "ras",
  "thresh" : 1.0e-8,
  "perturb" : 0.001,
  "perturb_min" : 1.0e-7,
  "perturb_thresh" : 1.0e-7,
  "ras" : {
    "nguess" : 5,
    "maxiter" : 50,
    "thresh" : 1.0e-8
  },
  "maxiter" : 50,
  "spaces" : [ [ {"charge" : 0, "nspin" : 0, "nstate" : 1},
                 {"charge" : 0, "nspin" : 2, "nstate" : 1},
                 {"charge" : 1, "nspin" : 1, "nstate" : 1},
                 {"charge" : -1, "nspin" : 1, "nstate" : 1} ] ],
  "restricted" : [ { "orbitals" : [ 1, 0, 4], "max_holes" : 1, "max_particles" : 1 } ]
}

]}

Reference

Description of Reference Reference
Active space decomposition with multiple sites: density matrix renormalization group algorithm S. M. Parker and T. Shiozaki, J. Chem. Phys. 141, 211102 (2014).