# 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.

### 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