hfx_ace_methods Module Reference

Adaptively Compressed Exchange (ACE) operator for HFX. Reference: Lin, J. Chem. Theory Comput. 2016, 12, 5, 2242-2249. More...

Functions/Subroutines
subroutine, public	hfx_ace_ks_matrix (qs_env, ks_matrix, rho, energy, calculate_forces, just_energy, v_rspace_new, v_tau_rspace, ace_rebuild_frequency, ext_xc_section)
	Main ACE entry point, replacing hfx_ks_matrix in qs_ks_methods.
subroutine, public	hfx_ace_release (iw_opt)
	Release all ACE storage and reset state flags.
subroutine, public	hfx_ace_set_dynamic_mode (is_dynamic)
	Mark this run as dynamic (GEO_OPT/MD) so Bypass C fires for geo step 0. Call this once from the geo_opt or MD driver before the first SCF.

Detailed Description

Adaptively Compressed Exchange (ACE) operator for HFX. Reference: Lin, J. Chem. Theory Comput. 2016, 12, 5, 2242-2249.

Algorithm (per spin):

BUILD (first call, or every rebuild_frequency steps):

1. Full HFX: ks_matrix = K_HFX + H_core, energyex = E_x(full)
2. K_AO = ks_matrix - H_core (nao x nao, negative semidefinite)
3. C_occ = first nocc columns of mo_coeff, redistributed to a layout compatible with K_AO so that PDGEMM works correctly
4. xi = K_AO * C_occ (nao x nocc)
5. M = C_occ^T * xi (nocc x nocc, negative definite)
6. -M = U^T U via Cholesky (U upper triangular, stored in M_fm)
7. W = xi * U^{-1} (nao x nocc, the ACE projector)
8. Apply (see below) to update ks_matrix and energyex

APPLY (all other steps): ks_matrix = H_core - W * W^T E_x = -0.5 * Tr[W^T * P * W]

Diagnostics (controlled by DBG_STALE / DBG_EXACT_EX module flags):

DIAG A projector staleness (cheap, runs every APPLY step) Computes ||W^T C_occ^current||_F / ||W^T C_occ^BUILD||_F. Ratio = 1 → W still accurate. Ratio -> 0 → W is stale.

DIAG B exact vs ACE exchange energy (expensive: one full HFX per APPLY) Calls full HFX with just_energy=.TRUE. to get E_x^exact[P^k] and compares to E_x^ACE[P^k]. Growing |delta| confirms stale W. ACE ks_matrix and energyex are restored after the diagnostic.

Author

Ritama Kar

Function/Subroutine Documentation

hfx_ace_ks_matrix()

subroutine, public hfx_ace_methods::hfx_ace_ks_matrix	(	type(qs_environment_type), pointer	qs_env,
		type(dbcsr_p_type), dimension(:, :), pointer	ks_matrix,
		type(qs_rho_type), pointer	rho,
		type(qs_energy_type), pointer	energy,
		logical, intent(in)	calculate_forces,
		logical, intent(in)	just_energy,
		type(pw_r3d_rs_type), dimension(:), pointer	v_rspace_new,
		type(pw_r3d_rs_type), dimension(:), pointer	v_tau_rspace,
		integer, intent(in)	ace_rebuild_frequency,
		type(section_vals_type), optional, pointer	ext_xc_section
	)

Main ACE entry point, replacing hfx_ks_matrix in qs_ks_methods.

Parameters

qs_env	...
ks_matrix	...
rho	...
energy	...
calculate_forces	...
just_energy	...
v_rspace_new	...
v_tau_rspace	...
ace_rebuild_frequency	...
ext_xc_section	...

Definition at line 147 of file hfx_ace_methods.F.

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hfx_ace_release()

subroutine, public hfx_ace_methods::hfx_ace_release

(

integer, intent(in), optional

iw_opt

)

Release all ACE storage and reset state flags.

Parameters

iw_opt

...

Definition at line 834 of file hfx_ace_methods.F.

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hfx_ace_set_dynamic_mode()

subroutine, public hfx_ace_methods::hfx_ace_set_dynamic_mode

(

logical, intent(in)

is_dynamic

)

Mark this run as dynamic (GEO_OPT/MD) so Bypass C fires for geo step 0. Call this once from the geo_opt or MD driver before the first SCF.

Parameters

is_dynamic

.TRUE. for GEO_OPT/MD, .FALSE. to reset.

...

Parameters

is_dynamic

...

Definition at line 871 of file hfx_ace_methods.F.

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