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fragment

Specify a fragment of a molecule/system by providing the indices of atoms, and optionally, the charge and spin. This command can appear in the global context.

Options

atoms

Specify the indices of atoms belonging to this fragment. The atoms are indexed from 1

  • The type is [int]
  • There is no default value.
  • The value must be positive
charge

Total charge on this fragment. Note that non-integer values are possible as well.

  • The type is real
  • The default is 0
multiplicity

Spin multiplicity - only valid for integer-electron calculations. For non-integer-electron number, or for higher multiplcities, use the spin option.

By default entos selects the lowest available spin multiplicity.

  • The type is string
  • There is no default value.
  • The value must be one of:
    • singlet - S = 0
    • doublet - S = 1/2
    • triplet - S = 1
    • quartet - S = 3/2
    • quintet - S = 2
    • sextet - S = 5/2
spin

For spin-unrestricted calculations, the spin \(2S\).

Notice that the value of this option need not be an integer. See the documentation on spin_z for an explanation.

By default entos selects the lowest available spin multiplicity.

  • The type is real
  • There is no default value.
  • The value must be nonnegative