pydmqmc.utils.get_double_perm
- pydmqmc.utils.get_double_perm(b1, a, b, r, s, nel)
Return new bitarray and the number of permutations for a double excitation.
- Parameters:
- b1array
The bitarray of the initial state.
- a, bint
The indices of the occupied orbitals to be vacated.
- r, sint
The indices of the unoccupied orbitals to be filled.
- nelint
The number of electrons in the system.
- Returns:
- array
The new bitarray after the excitation.
- int
The number of permutations associated with the excitation.