Dyson Orbitals

Description

Dyson orbitals are the effective one-particle wavefunctions for describing the ionization transition from a wavefunction with N electrons to one with N-1 electrons. They can be evaluated as the overlap between the initial and final wavefunction. Since those wavefunctions differ by one electron, the overlap is not a scalar but a one-particle wavefunction. The norm of the Dyson orbital indicates the intensity of the ionization channel. For Koopmans-allowed transitions the norm is close to 1 and close 0 for forbidden transitions.

Dyson orbitals require two calculations: one for the initial and one for the final wavefunctions. The wavefunctions have to be saved to files using the save_ref command.

Commands: dyson

Limitations

So far Dyson orbitals have been implemented only for CASSCF and CASPT2 wavefunctions.

Keywords

initial

Description: Specify initial N-electron wavefunctions.

Datatype: JSON

Keywords:

states

Description: list of state indices

Datatype: vector<int>

Default: [0], i.e. only ground state

file

Description: The initial wavefunctions, which were generated in a previous

calculation and saved via the save_ref command, are read in from this

file. The extension .archive will be appended.

Datatype: string

final

Description: Specify final (N-1)-electron wavefunctions.

Datatype: JSON

Keywords:

states

Description: list of state indices

Datatype: vector<int>

Default: [0], i.e. only ground state

file

Description: The final wavefunctions, which were generated in a previous

calculation and saved via the save_ref command, are read in from this

file. The extension .archive will be appended.

Datatype: string

thresh

Description: Threshold for neglecting products of CI coefficients in overlap calculations.

Datatype: double

Default: 1.0e-10

Recommendation: The calculation can be sped up by increasing this threshold.

molden_file

Description: File name for saving Dyson orbitals in molden format.

Datatype: string

Default: dyson_orbitals.molden

Example

Sample input

{ "bagel": [
 {
     "title": "molecule",
     "basis": "svp",
     "df_basis": "svp-jkfit",
     "angstrom": true,
     "geometry": [
         {"atom": "H", "xyz" : [ -0.227, -0.825, -2.666] },
         {"atom": "O", "xyz" : [  0.186, -0.147, -3.258] },
         {"atom": "H", "xyz" : [  0.030,  0.714, -2.796] }
     ]
 },

 {
     "title"   : "casscf",
     "nclosed" : 1,
     "nact"    : 6,
     "nstate"  : 3,
     "charge"  : 0,
     "nspin"   : 0
 },

 {
     "title" : "save_ref",
     "file"  : "h2o"
 },

 {
     "title"   : "casscf",
     "nclosed" : 1,
     "nact"    : 6,
     "nstate"  : 3,
     "charge"  : 1,
     "nspin"   : 1
 },

 {
     "title"  : "save_ref",
     "file"   : "h2o+"
 },

 {
     "title"   : "dyson",
     "initial" :
     {
         "states" : [0,1],
         "file"   : "h2o"
     },
     "final"   :
     {
         "states" : [0,1,2],
         "file"   : "h2o+"
     },
     "thresh"  : 1.0e-8,
     "molden_file" : "dyson_orbitals.molden"
 }
]}

References

Description of Reference	Reference
Dyson orbitals are expanded according to eqn. (22)	A. Humeniuk and M.Wohlgemuth and T. Suzuki and R.Mitric, J. Chem. Phys. 139, 134104 (2013)
Dyson orbitals (definition and some applications)	M. Oana and A. Krylov, J. Chem. Phys. 127, 234106 (2007).