Molecular grid settings

This section provides a reference for the settings related to molecular grids in GauXC, including C++ class definitions, C bindings, and Fortran bindings for creating and managing molecular grids used in numerical integration schemes.

C++ definitions

This section provides C++ class definitions provided by the gauxc/molgrid.hpp header.

class GauXC::MolGrid

Molecular integration grid container.

MolGrid aggregates atom-centered quadrature grids for each atomic number and exposes access to per-element grids and batch sizing information for numerical integration.

inline MolGrid GauXC::MolGridFactory::create_default_molgrid(const Molecule &mol, PruningScheme scheme, BatchSize bsz, RadialQuad radial_quad, AtomicGridSizeDefault grid_size)

Create a default MolGrid for the given molecule using the specified pruning scheme, batch size, radial quadrature, and atomic grid size. This constructor is available from the gauxc/molgrid/defaults.hpp header.

Parameters:

• mol – The molecule for which to create the MolGrid.

• scheme – The pruning scheme to use for constructing the molecular grid weights from the atomic grids.

• bsz – The batch size for processing grid points in parallel.

• radial_quad – The radial quadrature scheme to use for the atomic grids.

• grid_size – The default atomic grid size to use for the atomic grids.

Returns:

A MolGrid object initialized with the specified parameters for the given molecule.

inline MolGrid GauXC::MolGridFactory::create_default_molgrid(const Molecule &mol, PruningScheme scheme, BatchSize bsz, RadialQuad radial_quad, RadialSize rad_size, AngularSize ang_size)

Create a default MolGrid for the given molecule using the specified pruning scheme, batch size, radial quadrature, and explicit radial and angular sizes. This constructor is available from the gauxc/molgrid/defaults.hpp header.

Parameters:

• mol – The molecule for which to create the MolGrid.

• scheme – The pruning scheme to use for constructing the molecular grid weights from the atomic grids.

• bsz – The batch size for processing grid points in parallel.

• radial_quad – The radial quadrature scheme to use for the atomic grids.

• rad_size – The radial size to use for the atomic grids.

• ang_size – The angular size to use for the atomic grids.

Returns:

A MolGrid object initialized with the specified parameters for the given molecule.

The enumerator values are available from the gauxc/enums.hpp header.

enum class GauXC::AtomicGridSizeDefault

Enumeration of default atomic grid sizes for molecular integration.

The following options are available:

enumerator FineGrid

A default atomic grid size with 75 angular points and 302 radial points.

enumerator UltraFineGrid

A default atomic grid size with 99 angular points and 590 radial points.

enumerator SuperFineGrid

A default atomic grid size with 250 angular points and 974 radial points.

enumerator GM3

A default atomic grid size with 35 angular points and 110 radial points.

enumerator GM5

A default atomic grid size with 50 angular points and 302 radial points.

enum class GauXC::RadialQuad

Enumeration of radial quadrature schemes for atomic grids.

The following options are available:

enumerator Becke

The Becke radial quadrature scheme.[1]

enumerator MuraKnowles

The Mura-Knowles radial quadrature scheme.[2]

enumerator TreutlerAhlrichs

The Treutler-Ahlrichs radial quadrature scheme.[3]

enumerator MurrayHandyLaming

The Murray-Handy-Laming radial quadrature scheme.[4]

enum class GauXC::PruningScheme

Enumeration of pruning schemes for constructing molecular grid weights from atomic grids.

The following options are available:

enumerator Unpruned

No pruning is applied to the atomic grids when constructing the molecular grid.

enumerator Robust

Robust pruning scheme from Psi4.

enumerator Treutler

The Treutler pruning scheme.

using GauXCRadialSize = int64_t

Type to represent the number of radial points in an atomic grid.

using GauXCAngularSize = int64_t

Type to represent the number of angular points in an atomic grid.

using GauXC::BatchSize = int64_t

Defines the batch size for processing grid points in parallel. Default is 512 points per batch, however larger values up around 10000 are recommended for better performance.

C bindings

The following C bindings are available in the gauxc/molgrid.h header for creating and managing molecular grids in the GauXC C API.

struct GauXCMolGrid

Opaque struct representing a molecular grid in the GauXC C API.

GauXCMolGrid gauxc_molgrid_new_default(GauXCStatus *status, const GauXCMolecule *molecule, enum GauXC_PruningScheme pruning_scheme, int64_t batch_size, enum GauXC_RadialQuad radial_quad, enum GauXC_AtomicGridSizeDefault grid_size)

Create a new GauXCMolGrid object with default settings for the given molecule.

Parameters:

• status – Pointer to a GauXCStatus variable to store the status of the operation.

• molecule – Pointer to a GauXCMolecule object representing the molecule for which to create the MolGrid.

• pruning_scheme – The pruning scheme to use for constructing the molecular grid weights from the atomic grids.

• batch_size – The batch size for processing grid points in parallel.

• radial_quad – The radial quadrature scheme to use for the atomic grids.

• grid_size – The default atomic grid size to use for the atomic grids.

Returns:

A new GauXCMolGrid object initialized with the specified parameters for the given molecule.

void gauxc_molgrid_delete(GauXCStatus *status, GauXCMolGrid *molgrid)

Delete a GauXCMolGrid object and free its resources.

Parameters:

• status – Pointer to a GauXCStatus variable to store the status of the operation.

• molgrid – Pointer to the GauXCMolGrid object to delete.

enum GauXC_PruningScheme

Enumeration of pruning schemes for constructing molecular grid weights from atomic grids in the GauXC C API.

The following options are available:

enumerator GauXC_PruningScheme_Unpruned

No pruning is applied to the atomic grids when constructing the molecular grid.

enumerator GauXC_PruningScheme_Robust

Robust pruning scheme from Psi4.

enumerator GauXC_PruningScheme_Treutler

The Treutler pruning scheme.

enum GauXC_RadialQuad

Enumeration of radial quadrature schemes for atomic grids in the GauXC C API.

The following options are available:

enumerator GauXC_RadialQuad_Becke

The Becke radial quadrature scheme.[1]

enumerator GauXC_RadialQuad_MuraKnowles

The Mura-Knowles radial quadrature scheme.[2]

enumerator GauXC_RadialQuad_TreutlerAhlrichs

The Treutler-Ahlrichs radial quadrature scheme.[3]

enumerator GauXC_RadialQuad_MurrayHandyLaming

The Murray-Handy-Laming radial quadrature scheme.[4]

enum GauXC_AtomicGridSizeDefault

Enumeration of default atomic grid sizes for molecular integration in the GauXC C API.

The following options are available:

enumerator GauXC_AtomicGridSizeDefault_FineGrid

A default atomic grid size with 75 angular points and 302 radial points.

enumerator GauXC_AtomicGridSizeDefault_UltraFineGrid

A default atomic grid size with 99 angular points and 590 radial points.

enumerator GauXC_AtomicGridSizeDefault_SuperFineGrid

A default atomic grid size with 250 angular points and 974 radial points.

enumerator GauXC_AtomicGridSizeDefault_GM3

A default atomic grid size with 35 angular points and 110 radial points.

enumerator GauXC_AtomicGridSizeDefault_GM5

A default atomic grid size with 50 angular points and 302 radial points.

Fortran bindings

type  gauxc_molgrid_type

Opaque type representing a molecular grid in the GauXC Fortran API. Available in the module gauxc_molgrid.

function gauxc_molgrid_new_default(status, molecule, pruning_scheme, batch_size, radial_quad, grid_size)

Parameters:

• status [type(gauxc_status_type)] :: Output parameter to store the status of the operation.

• molecule [type(gauxc_molecule_type)] :: The molecule for which to create the MolGrid.

• pruning_scheme [integer(c_int)] :: The pruning scheme to use for constructing the molecular grid weights from the atomic grids.

• batch_size [integer(c_int64_t)] :: The batch size for processing grid points in parallel.

• radial_quad [integer(c_int)] :: The radial quadrature scheme to use for the atomic grids.

• grid_size [integer(c_int)] :: The default atomic grid size to use for the atomic grids.

Return:

type (gauxc_molgrid_type) :: A new gauxc_molgrid_type object initialized with the specified parameters for the given molecule.

subroutine gauxc_molgrid_delete(status, molgrid)

Delete a gauxc_molgrid_type object and free its resources. Part of the gauxc_delete() interface.

Parameters:

• status [type(gauxc_status_type)] :: Output parameter to store the status of the operation.

• molgrid [type(gauxc_molgrid_type)] :: The gauxc_molgrid_type object to delete.

type  gauxc_radialquad

Parameter instance of a derived type with the respective enumerator values for each member variable.

Type fields:

• % becke [integer(c_int)] :: The Becke radial quadrature scheme.[1]

• % muraknowles [integer(c_int)] :: The Mura-Knowles radial quadrature scheme.[2]

• % treutlerahlrichs [integer(c_int)] :: The Treutler-Ahlrichs radial quadrature scheme.[3]

• % murrayhandylaming [integer(c_int)] :: The Murray-Handy-Laming radial quadrature scheme.[4]

type  gauxc_pruningscheme

Parameter instance of a derived type with the respective enumerator values for each member variable.

Type fields:

• % unpruned [integer(c_int)] :: No pruning is applied to the atomic grids when constructing the molecular grid.

• % robust [integer(c_int)] :: Robust pruning scheme from Psi4.

• % treutler [integer(c_int)] :: The Treutler pruning scheme.

type  gauxc_atomicgridsizedefault

Parameter instance of a derived type with the respective enumerator values for each member variable.

Type fields:

• % finegrid [integer(c_int)] :: A default atomic grid size with 75 angular points and 302 radial points.

• % ultrafinegrid [integer(c_int)] :: A default atomic grid size with 99 angular points and 590 radial points.

• % superfinegrid [integer(c_int)] :: A default atomic grid size with 250 angular points and 974 radial points.

• % gm3 [integer(c_int)] :: A default atomic grid size with 35 angular points and 110 radial points.

• % gm5 [integer(c_int)] :: A default atomic grid size with 50 angular points and 302 radial points.

References

[1] (1,2,3)

Axel D Becke. A multicenter numerical integration scheme for polyatomic molecules. The Journal of chemical physics, 88(4):2547–2553, 1988. doi:10.1063/1.454033.

[2] (1,2,3)

Michael E Mura and Peter J Knowles. Improved radial grids for quadrature in molecular density-functional calculations. The Journal of Chemical Physics, 104(24):9848–9858, 1996. doi:10.1063/1.471749.

[3] (1,2,3)

Oliver Treutler and Reinhart Ahlrichs. Efficient molecular numerical integration schemes. The Journal of Chemical Physics, 102(1):346–354, 1995. doi:10.1063/1.469408.

[4] (1,2,3)

Christopher W Murray, Nicholas C Handy, and Gregory J Laming. Quadrature schemes for integrals of density functional theory. Molecular Physics, 78(4):997–1014, 1993. doi:10.1080/00268979300100651.