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)
	Compute the expectation value <(\cal S)^2> of the single determinant defined by the spin up (alpha) and spin down (beta) orbitals.
subroutine, public	compute_s_square_kp (mosin, kpoints, matrix_s, s_square, s_square_ideal)
	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 )

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

History

07.2004 created (Joost VandeVondele) 08.2021 revised (Matthias Krack, MK) 10.2026 adapted and generalized to partial occupation and k-points

Note

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

Definition at line 97 of file s_square_methods.F.

Here is the call graph for this function:

Here is the caller graph for this function:

compute_s_square_kp()

subroutine, public s_square_methods::compute_s_square_kp	(	type(mo_set_type), dimension(:), intent(in)	mosin,
		type(kpoint_type), intent(in), pointer	kpoints,
		type(dbcsr_p_type), dimension(:, :), pointer	matrix_s,
		real(kind=dp), intent(out)	s_square,
		real(kind=dp), intent(out)	s_square_ideal )

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

Parameters

mosin	...
kpoints	...
matrix_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

History

10.2026 adapted and generalized to partial occupation and k-points

Definition at line 157 of file s_square_methods.F.

Here is the call graph for this function:

Here is the caller graph for this function:

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 315 of file s_square_methods.F.

Here is the call graph for this function:

Here is the caller graph for this function: