The per-point XC kernel API

Classes
struct	excgrid::XcKernelValue
class	excgrid::XcFunctional

Typedefs
using	excgrid::LdaKernel = XcKernelValue (*)(double rhoA, double rhoB)
using	excgrid::GgaKernel

Functions
constexpr XcKernelValue	excgrid::operator+ (const XcKernelValue &a, const XcKernelValue &b) noexcept
constexpr XcKernelValue &	excgrid::operator+= (XcKernelValue &a, const XcKernelValue &b) noexcept
constexpr XcKernelValue	excgrid::operator* (double weight, const XcKernelValue &v) noexcept
constexpr XcKernelValue	excgrid::operator* (const XcKernelValue &v, double weight) noexcept
const XcFunctional *	excgrid::FindFunctional (std::string_view name) noexcept
std::span< const std::string_view >	excgrid::FunctionalNames () noexcept

Detailed Description

The frozen seam between excgrid's functionals and their consumers (docs/kernel-api.md is the governing contract; this header is its implementation). Units are Libxc's everywhere: densities in electrons/Bohr^3, sigma in Bohr^-8, energy densities in Hartree/Bohr^3, potentials in Hartree (vrho) and Hartree * Bohr^5 (vsigma).

Typedef Documentation

GgaKernel

using excgrid::GgaKernel

Initial value:

 
XcKernelValue (*)(double rhoA, double rhoB, double sigmaAa, double sigmaAb, double sigmaBb)

GGA kernel: additionally consumes the three sigma inputs and returns the three vsigma derivatives.

LdaKernel

using excgrid::LdaKernel = XcKernelValue (*)(double rhoA, double rhoB)

LDA kernel: the energy density and its spin-density derivatives.

Function Documentation

FindFunctional()

const XcFunctional * excgrid::FindFunctional ( std::string_view name )

noexcept

Resolves a functional by its shipped name (docs/kernel-api.md section 4); null when unknown. Name-string resolution, never an enum - enums drift with repo releases, the consumer's schema carries the string.

Parameters

name	The functional name.

Returns

The functional, or nullptr.

FunctionalNames()

std::span< const std::string_view > excgrid::FunctionalNames ( )

noexcept

All shipped functional names, registry order.

Returns

The name span (owned by the registry).

operator*() [1/2]

XcKernelValue excgrid::operator* ( const XcKernelValue & v, double weight )

constexprnoexcept

Scalar weighting, mirrored order.

Parameters

v	The weighted value.
weight	The scalar weight.

Returns

The componentwise product.

operator*() [2/2]

XcKernelValue excgrid::operator* ( double weight, const XcKernelValue & v )

constexprnoexcept

Scalar weighting - functional composition by * (hybrid recipes).

Parameters

weight	The scalar weight.
v	The weighted value.

Returns

The componentwise product.

operator+()

XcKernelValue excgrid::operator+ ( const XcKernelValue & a, const XcKernelValue & b )

constexprnoexcept

Componentwise addition - functional composition by +.

Parameters

a	The first summand.
b	The second summand.

Returns

The componentwise sum.

operator+=()

XcKernelValue & excgrid::operator+= ( XcKernelValue & a, const XcKernelValue & b )

constexprnoexcept

Componentwise accumulation.

Parameters

a	The accumulator (updated).
b	The addend.

Returns

The updated accumulator.