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excited_scf

Performs an scf calculation to obtain one or more excited states. For example:

excited_scf(structure(molecule = water) xtb())
will perform a delta-scf calculation for water at the GFN1-xTB level of theory. This command can appear in the global context.

Subcommands

Options

average

Optionally compute state using Slater's transition method (average = 'density'). This builds the density with half an electron in each of the ground-state and excited orbitals during the SCF procedure.

  • The type is string
  • The default is none
excitation

Orbitals from which the electron is taken and moved to, specified by orbital number relative to overall initial HOMO. That is:

HOMO = 0,

LUMO = 1,

Requires unrestricted SCF to work (ansatz = u).

  • The type is [int]
  • The default is [0, 1]
method

the method use to calculate the excited state

  • The type is string
  • The default is delta_scf
  • The value must be one of:
    • delta_scf - Use the delta-scf method. Using the ground state as the initial guess, one electron is promoted to a virtual orbital and another scf cycle is done. For singlet state, the spin purification formula is used. See https://doi.org/10.1021/jp801738f for details on delta-scf, as well as it's use with the maximum overlap method.
occupied_spin

Spin of the orbital from which the electron is taken

  • The type is string
  • The default is beta
  • The value must be one of:
    • alpha - Spin alpha
    • beta - Spin beta
print_level

Print level.

  • The type is int
  • There is no default value.
  • The value must be one of:
    • -2 - No output
    • -1 - Minimum output
    • 0 - Output that doesn't scale with system size
    • 1 - Output that scales linearly with system size
    • 2 - (Debugging) output that scales quadratically with system size
    • 3 - (Debugging) output that scales cubically with system size
spin_flip

Specify whether or not to flip the spin of the excited electron

  • The type is bool
  • The default is false
use_mom

Override for the mom switch in dft(). In excited_scf, the maximum overlap method is strongly recommended, thus the default is true in this case. When using excited_scf, the mom keyword of the given method is ignored and this use_mom flag is used instead.

  • The type is bool
  • The default is true