s_square_methods Module Reference

Methods related to (\cal S)^2 (i.e. spin) More...

Functions/Subroutines
subroutine, public	compute_s_square (mos, matrix_s, s_square, s_square_ideal, mo_derivs, strength)
	Compute the expectation value <(\cal S)^2> of the single determinant defined by the spin up (alpha) and spin down (beta) orbitals.
subroutine, public	s2_restraint (mos, matrix_s, mo_derivs, energy, s2_restraint_control, just_energy)
	restrains/constrains the value of s2 in a calculation

Detailed Description

Methods related to (\cal S)^2 (i.e. spin)

History

03.2006 copied compute_s_square from qs_scf_post (Joost VandeVondele) 08.2021 revised (Matthias Krack, MK)

Author

Joost VandeVondele

Function/Subroutine Documentation

compute_s_square()

subroutine, public s_square_methods::compute_s_square	(	type(mo_set_type), dimension(:), intent(in)	mos,
		type(dbcsr_p_type), dimension(:), pointer	matrix_s,
		real(kind=dp), intent(out)	s_square,
		real(kind=dp), intent(out)	s_square_ideal,
		type(cp_fm_type), dimension(:), intent(inout), optional	mo_derivs,
		real(kind=dp), intent(in), optional	strength
	)

Compute the expectation value <(\cal S)^2> of the single determinant defined by the spin up (alpha) and spin down (beta) orbitals.

Parameters

mos	[in] MO set with all MO information including the alpha and beta MO coefficients
matrix_s	[in] AO overlap matrix S (do not mix with the spin operator (\cal S))
s_square	[out] <(\cal S)^2> including potential spin contaminations
s_square_ideal	[out] Ideal value for <(\cal S)^2> without any spin contaminations
mo_derivs	[inout] If present, add the derivative of s_square wrt the MOs to mo_derivs
strength	[in] Strength for constraining or restraining (\cal S)^2

History

07.2004 created (Joost VandeVondele) 08.2021 revised (Matthias Krack, MK)

Note

See Eqs. 2.271 and 2.272 in Modern Quantum Chemistry by A. Szabo and N. S. Ostlund

Definition at line 65 of file s_square_methods.F.

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s2_restraint()

subroutine, public s_square_methods::s2_restraint	(	type(mo_set_type), dimension(:), intent(in)	mos,
		type(dbcsr_p_type), dimension(:), pointer	matrix_s,
		type(cp_fm_type), dimension(:), intent(inout)	mo_derivs,
		real(kind=dp)	energy,
		type(s2_restraint_type), pointer	s2_restraint_control,
		logical	just_energy
	)

restrains/constrains the value of s2 in a calculation

Parameters

mos	input
matrix_s	input
mo_derivs	inout if present, add the derivative of s_square wrt mos to mo_derivs
energy	...
s2_restraint_control	...
just_energy	...

History

07.2004 created [ Joost VandeVondele ]

Definition at line 189 of file s_square_methods.F.

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