quantum mechanics/quantum chemistry functionality including Hartree-Fock and more More...

Namespaces
namespace	cc
namespace	cint
namespace	cphf
	Coupled-perturbed SCF (CPHF / CPKS).
namespace	impl
namespace	guess
namespace	block
namespace	orb
namespace	cosx
namespace	basis_sets

Classes
class	ADIIS
	ADIIS (Augmented Direct Inversion in Iterative Subspace) Based on Hu & Yang, J. More...
struct	AutoAuxResult
	Statistics about the auto auxiliary basis generation. More...
class	CDIIS
class	ConvergenceAccelerator
	Encapsulates SCF convergence acceleration strategies (CDIIS, EDIIS, ADIIS). More...
class	DFIntegrals
	Builds metric-folded density-fitting "B" tensors for correlated methods. More...
class	MOIntegralEngine
	Lightweight holder of molecular-orbital information for post-HF methods, plus a brute-force single MO electron-repulsion integral evaluator kept as a reference/testing utility. More...
class	MP2
class	PostHFMethod
class	CoulombMetric
	Factorization of a density-fitting Coulomb metric V = (P\|Q). More...
class	PackedDFStore
	Three-centre integrals (μν\|P) over the screened canonical shell pairs (q <= p, as IntegralEngine::shellpairs()), packed: one contiguous np x nq block per stored shell pair, every auxiliary function a column. More...
class	EDIIS
struct	PointChargePotential
	Plain external point charges (vacuum Coulomb). More...
struct	WolfPointChargePotential
	Wolf-summed periodic point charges. More...
class	GradientEvaluator
class	HessianEvaluator
	Evaluates molecular Hessian matrices (second derivatives of energy). More...
struct	COSXGridSchedule
	ORCA's COSX grid schedule: iterate on a coarse grid, switch to a finer one once the SCF is close (DIIS error below refine_threshold, or converged on the coarse grid), and evaluate the final exchange energy once on the final grid. More...
class	HartreeFock
struct	GuessRequest
	What a guess needs to know about the system. More...
struct	Guess
	The starting point a guess produces. More...
struct	JKPair
struct	JKTriple
class	IntegralEngine
class	ScopedRangeSeparation
	Applies a range-separation parameter for the duration of a scope, and puts back whatever was there before however the scope is left. More...
class	IntegralEngineDF
struct	PipekMezeySettings
struct	LocalizedOrbitals
	Orbitals localized by an orthogonal rotation of the input set. More...
struct	MolecularOrbitals
struct	Oniom
struct	OrbitalSmearing
class	CanonicalOrthogonalizer
struct	SCFContext
struct	SCF
struct	SCFConvergenceSettings
struct	FockBuildProperties
	What a method guarantees about its Fock build, so the SCF driver can decide whether to accumulate F += G(ΔD) instead of rebuilding from H each cycle. More...
class	SCFMethodBase
class	SplitRIJ
	Split-RI-J: Coulomb matrix via Hermite Gaussian basis (Neese 2003). More...
struct	Energy
struct	Wavefunction
class	AOBasis
struct	Shell
class	FchkReader
class	FchkWriter
class	MoldenReader
	Reader for Molden format wavefunction files. More...
class	OrcaJSONReader

Concepts
concept	ExternalPotential
	Concept for an external-potential model: a self-contained engine that produces a one-electron potential matrix V_ext and the nuclear–external interaction energy when handed an SCF procedure (HF/DFT/etc.).
concept	AnalyticHessianProcedure
	A procedure that provides every term the analytic Hessian needs.
concept	SCFMethod
concept	DensityFittingMethod
concept	PointChargeMethod

Typedefs
using	PointChargeList = std::vector<occ::core::PointCharge>
using	DispersionGradientFunc
	Callback that computes a dispersion energy and nuclear gradient for the given basis / orbitals / charge.
using	HessianMatrix = Mat
using	ShellPairList = std::vector<std::vector<size_t>>
using	Vec
using	Vec

Enumerations
enum class	FittingKind { JK , J , Correlation }
enum class	DispersionType { None , D4 }
enum class	GuessKind { Auto , Core , Soad , Sap , AtomicScf }
	Where the SCF starts from. More...
enum class	CoulombMethod { Traditional , SplitRIJ }
	Method for computing Coulomb matrix in density fitting. More...
enum class	PopulationKind { Mulliken , Lowdin }
	Atomic population entering the Pipek-Mezey functional. More...
enum class	DiisStrategy { CDIIS , EDIIS_CDIIS , ADIIS_CDIIS }
	Strategy for DIIS extrapolation during SCF. More...
enum class	SpinComponent { Total , Alpha , Beta }
enum	SpinorbitalKind
	Spin treatment for molecular orbitals / SCF. More...

Functions
AutoAuxResult	generate_auto_aux (const AOBasis &basis, double threshold=1e-7, std::optional< int > max_l=std::nullopt)
	Generate automatic auxiliary basis using pivoted Cholesky decomposition Based on Lehtola, J.
Vec	chelpg_charges (const Wavefunction &wfn)
template<SpinorbitalKind kind, typename TA>
TA::Scalar	expectation (const TA &left, const TA &right)
template<typename TA>
TA::Scalar	expectation (SpinorbitalKind sk, const TA &left, const TA &right)
std::string	resolve_fitting_basis (const std::string &orbital_basis_name, FittingKind kind)
int	cosx_nbf_crossover ()
std::string_view	guess_kind_name (GuessKind kind)
const std::vector< std::pair< std::string, GuessKind > > &	guess_kind_names ()
	The names a user may write, and what each selects.
std::optional< GuessKind >	guess_kind_from_string (std::string_view name)
	Parse a guess name. Returns nothing for an unrecognised one.
bool	minimal_basis_covers (const gto::AOBasis &basis)
	Whether the shipped minimal basis has shells for every atom in basis.
GuessKind	select_guess (GuessKind requested, const gto::AOBasis &basis)
	Resolve Auto into a concrete kind; anything else passes through unchanged, so an explicit request is honoured even where it is a poor choice.
Guess	build_guess (GuessKind kind, const GuessRequest &request)
	Build kind for request.
template<typename T>
	ScopedRangeSeparation (T &, double) -> ScopedRangeSeparation< T >
void	from_json (const nlohmann::json &J, Energy &energy)
void	to_json (nlohmann::json &J, const Energy &energy)
void	from_json (const nlohmann::json &J, Wavefunction &wfn)
void	to_json (nlohmann::json &J, const Wavefunction &wfn)
LocalizedOrbitals	pipek_mezey (const AOBasis &basis, const Mat &S, const Mat &C, const PipekMezeySettings &settings={})
	Pipek-Mezey localization (Pipek & Mezey, JCP 90, 4916 (1989)) of the columns of C by Jacobi sweeps: maximizes sum_k sum_A (q_A^k)^2, the atomic populations of each orbital, over rotations among the columns of C.
LocalizedOrbitals	pipek_mezey (const Wavefunction &wfn, int n_frozen=0, const PipekMezeySettings &settings={})
	Pipek-Mezey localization of the occupied orbitals of a closed-shell restricted wavefunction, the n_frozen lowest left out.
std::pair< Mat, Vec >	merge_molecular_orbitals (const Mat &, const Mat &, const Vec &, const Vec &, bool sort_by_energy=false)
AOBasis	merge_basis_sets (const AOBasis &, const AOBasis &)
std::vector< occ::core::Atom >	merge_atoms (const std::vector< occ::core::Atom > &, const std::vector< occ::core::Atom > &)
Vec	mulliken_partition (const AOBasis &basis, const MolecularOrbitals &mo, Eigen::Ref< const Mat > op)
constexpr bool	supports_incremental_fock_build (const FockBuildProperties &properties)
	F can only be accumulated when the build is linear and the core Hamiltonian is fixed; screening decides whether it is worth doing.
template<SpinorbitalKind sk, Shell::Kind kind>
Mat	shellblock_norm (const AOBasis &basis, const Mat &matrix) noexcept
template<SpinorbitalKind kind>
constexpr std::pair< size_t, size_t >	matrix_dimensions (size_t nbf)
constexpr std::pair< size_t, size_t >	matrix_dimensions (SpinorbitalKind kind, size_t nbf)
template<SpinorbitalKind kind, typename TA>
TA::Scalar	expectation (const TA &left, const TA &right)
template<typename T>
constexpr bool	is_odd (T a)
bool	get_spinorbital_kind_from_string (const std::string &s, SpinorbitalKind &sk)
constexpr const char *	spinorbital_kind_to_string (const SpinorbitalKind &sk)

Variables
template<typename T>
constexpr bool	is_scf_method_v = SCFMethod<T>
template<typename T>
constexpr bool	supports_density_fitting_v = DensityFittingMethod<T>
template<typename T>
constexpr bool	supports_point_charges_v = PointChargeMethod<T>
constexpr auto	OCC_MINIMAL_BASIS

Detailed Description

quantum mechanics/quantum chemistry functionality including Hartree-Fock and more

Typedef Documentation

◆ DispersionGradientFunc

using occ::qm::DispersionGradientFunc

Initial value:

std::function<std::pair<double, Mat3N>(

const AOBasis &, const MolecularOrbitals &, int)>

occ::gto::AOBasis

Definition shell.h:72

occ::qm::MolecularOrbitals

Definition mo.h:10

Callback that computes a dispersion energy and nuclear gradient for the given basis / orbitals / charge.

Used to inject corrections (e.g. XDM) that live in libraries above occ_qm, so occ_qm need not depend on them.

◆ HessianMatrix

using occ::qm::HessianMatrix = Mat

◆ PointChargeList

typedef std::vector< occ::core::PointCharge > occ::qm::PointChargeList = std::vector<occ::core::PointCharge>

◆ ShellPairList

using occ::qm::ShellPairList = std::vector<std::vector<size_t>>

◆ Vec [1/2]

using occ::Vec

◆ Vec [2/2]

using occ::Vec

Enumeration Type Documentation

◆ CoulombMethod

enum class occ::qm::CoulombMethod

strong

Method for computing Coulomb matrix in density fitting.

Enumerator
Traditional	libcint 3-center integrals (default)
SplitRIJ	MMD kernels using Hermite basis (no atomics).

◆ DiisStrategy

enum class occ::qm::DiisStrategy

strong

Strategy for DIIS extrapolation during SCF.

Enumerator
CDIIS	Standard commutator DIIS only.
EDIIS_CDIIS	EDIIS early, switch to CDIIS when error is small.
ADIIS_CDIIS	ADIIS early, switch to CDIIS when error is small (recommended).

◆ DispersionType

enum class occ::qm::DispersionType

strong

Enumerator
None
D4

◆ FittingKind

enum class occ::qm::FittingKind

strong

Enumerator
JK
J
Correlation

◆ GuessKind

enum class occ::qm::GuessKind

strong

Where the SCF starts from.

Every kind here ends in the same place – diagonalise a Fock matrix built from something cheaper than the answer – and differs only in what that something is. See <occ/qm/initial_guess.h> for how each is built.

This lives apart from the rest of the guess API, and depends on nothing, so that input handling can name a guess without taking on a dependency on the SCF itself.

Enumerator
Auto	Choose per system; see select_guess.
Core	No guess: diagonalise the bare core Hamiltonian. Always available, and always the worst starting point that still converges.
Soad	Superposition of atomic densities: tabulated ground-state occupations spread over a minimal basis, projected into the orbital basis. Cheap and good, but only for elements the shipped minimal basis covers.
Sap	Superposition of atomic potentials: a fitted effective potential per element added to the core Hamiltonian. Covers every element, but has no sound treatment of effective core potentials.
AtomicScf	Superposition of converged isolated-atom densities, one small SCF per element in this calculation's own basis. Costs more than the others and works wherever the orbital basis does, ECPs included.

◆ PopulationKind

enum class occ::qm::PopulationKind

strong

Atomic population entering the Pipek-Mezey functional.

Enumerator
Mulliken	qA = sum{mu in A} C_mu (S C)_mu, the original PM choice
Lowdin	qA = sum{mu in A} (S^1/2 C)_mu^2, never negative

◆ SpinComponent

enum class occ::qm::SpinComponent

strong

Enumerator
Total
Alpha
Beta

◆ SpinorbitalKind

enum occ::core::SpinorbitalKind

Spin treatment for molecular orbitals / SCF.

Unscoped enum: the enumerators are intentionally usable unqualified within the enclosing namespace. The canonical definition lives here (occ_core) so that low-level consumers (e.g. input/config structs) can reference it without depending on occ_qm; occ::qm re-exports the type and enumerators for backwards compatibility (see occ/qm/spinorbital.h).

Function Documentation

◆ build_guess()

Guess occ::qm::build_guess	(	GuessKind	kind,
		const GuessRequest &	request )

Build kind for request.

Falls back to Core – an empty Guess – when the guess cannot be built for this system, having said why in the log. Every caller therefore gets a usable starting point.

◆ chelpg_charges()

Vec occ::qm::chelpg_charges ( const Wavefunction & wfn )

◆ cosx_nbf_crossover()

int occ::qm::cosx_nbf_crossover ( )

◆ expectation() [1/3]

template<SpinorbitalKind kind, typename TA>

TA::Scalar occ::qm::expectation	(	const TA &	left,
		const TA &	right )

◆ expectation() [2/3]

template<SpinorbitalKind kind, typename TA>

TA::Scalar occ::qm::expectation	(	const TA &	left,
		const TA &	right )

◆ expectation() [3/3]

template<typename TA>

TA::Scalar occ::qm::expectation	(	SpinorbitalKind	sk,
		const TA &	left,
		const TA &	right )

◆ from_json() [1/2]

void occ::qm::from_json	(	const nlohmann::json &	J,
		Energy &	energy )

◆ from_json() [2/2]

void occ::qm::from_json	(	const nlohmann::json &	J,
		Wavefunction &	wfn )

◆ generate_auto_aux()

AutoAuxResult occ::qm::generate_auto_aux	(	const AOBasis &	basis,
		double	threshold = 1e-7,
		std::optional< int >	max_l = std::nullopt )

Generate automatic auxiliary basis using pivoted Cholesky decomposition Based on Lehtola, J.

Chem. Theory Comput. 2021, 17, 6886-6900

◆ get_spinorbital_kind_from_string()

bool occ::core::get_spinorbital_kind_from_string	(	const std::string &	s,
		SpinorbitalKind &	sk )

inline

◆ guess_kind_from_string()

std::optional< GuessKind > occ::qm::guess_kind_from_string ( std::string_view name )

inline

Parse a guess name. Returns nothing for an unrecognised one.

◆ guess_kind_name()

std::string_view occ::qm::guess_kind_name ( GuessKind kind )

inline

◆ guess_kind_names()

const std::vector< std::pair< std::string, GuessKind > > & occ::qm::guess_kind_names ( )

inline

The names a user may write, and what each selects.

Shared by the command line and by any other input route, so they cannot drift apart.

◆ is_odd()

template<typename T>

bool occ::util::is_odd ( T a )

constexpr

◆ matrix_dimensions() [1/2]

template<SpinorbitalKind kind>

std::pair< size_t, size_t > occ::qm::matrix_dimensions ( size_t nbf )

constexpr

◆ matrix_dimensions() [2/2]

std::pair< size_t, size_t > occ::qm::matrix_dimensions	(	SpinorbitalKind	kind,
		size_t	nbf )

inlineconstexpr

◆ merge_atoms()

std::vector< occ::core::Atom > occ::qm::merge_atoms	(	const std::vector< occ::core::Atom > &	,
		const std::vector< occ::core::Atom > &	)

◆ merge_basis_sets()

AOBasis occ::qm::merge_basis_sets	(	const AOBasis &	,
		const AOBasis &	)

◆ merge_molecular_orbitals()

std::pair< Mat, Vec > occ::qm::merge_molecular_orbitals	(	const Mat &	,
		const Mat &	,
		const Vec &	,
		const Vec &	,
		bool	sort_by_energy = false )

◆ minimal_basis_covers()

bool occ::qm::minimal_basis_covers ( const gto::AOBasis & basis )

Whether the shipped minimal basis has shells for every atom in basis.

build_sto3g_shells drops elements it has no entry for rather than failing, so loading the minimal basis is not itself a coverage test: an uncovered atom simply comes back carrying no shells.

◆ mulliken_partition()

Vec occ::qm::mulliken_partition	(	const AOBasis &	basis,
		const MolecularOrbitals &	mo,
		Eigen::Ref< const Mat >	op )

◆ pipek_mezey() [1/2]

LocalizedOrbitals occ::qm::pipek_mezey	(	const AOBasis &	basis,
		const Mat &	S,
		const Mat &	C,
		const PipekMezeySettings &	settings = {} )

Pipek-Mezey localization (Pipek & Mezey, JCP 90, 4916 (1989)) of the columns of C by Jacobi sweeps: maximizes sum_k sum_A (q_A^k)^2, the atomic populations of each orbital, over rotations among the columns of C.

The span of C is unchanged; S is the AO overlap.

◆ pipek_mezey() [2/2]

LocalizedOrbitals occ::qm::pipek_mezey	(	const Wavefunction &	wfn,
		int	n_frozen = 0,
		const PipekMezeySettings &	settings = {} )

Pipek-Mezey localization of the occupied orbitals of a closed-shell restricted wavefunction, the n_frozen lowest left out.

◆ resolve_fitting_basis()

std::string occ::qm::resolve_fitting_basis	(	const std::string &	orbital_basis_name,
		FittingKind	kind )

◆ ScopedRangeSeparation()

template<typename T>

occ::qm::ScopedRangeSeparation	(	T &	,
		double	)->ScopedRangeSeparation< T >

◆ select_guess()

GuessKind occ::qm::select_guess	(	GuessKind	requested,
		const gto::AOBasis &	basis )

Resolve Auto into a concrete kind; anything else passes through unchanged, so an explicit request is honoured even where it is a poor choice.

Logs the reason whenever Auto picks something other than SOAD.

◆ shellblock_norm()

template<SpinorbitalKind sk, Shell::Kind kind>

Mat occ::qm::shellblock_norm	(	const AOBasis &	basis,
		const Mat &	matrix )

inlinenoexcept

◆ spinorbital_kind_to_string()

const char * occ::core::spinorbital_kind_to_string ( const SpinorbitalKind & sk )

constexpr

◆ supports_incremental_fock_build()

bool occ::qm::supports_incremental_fock_build ( const FockBuildProperties & properties )

constexpr

F can only be accumulated when the build is linear and the core Hamiltonian is fixed; screening decides whether it is worth doing.

◆ to_json() [1/2]

void occ::qm::to_json	(	nlohmann::json &	J,
		const Energy &	energy )

◆ to_json() [2/2]

void occ::qm::to_json	(	nlohmann::json &	J,
		const Wavefunction &	wfn )

Variable Documentation

◆ is_scf_method_v

template<typename T>

bool occ::qm::is_scf_method_v = SCFMethod<T>

constexpr

◆ OCC_MINIMAL_BASIS

auto occ::gto::OCC_MINIMAL_BASIS

constexpr

◆ supports_density_fitting_v

template<typename T>

bool occ::qm::supports_density_fitting_v = DensityFittingMethod<T>

constexpr

◆ supports_point_charges_v

template<typename T>

bool occ::qm::supports_point_charges_v = PointChargeMethod<T>

constexpr

Namespaces

Classes

Concepts

Typedefs

Enumerations

Functions

Variables

Detailed Description

Typedef Documentation

◆ DispersionGradientFunc

◆ HessianMatrix

◆ PointChargeList

◆ ShellPairList

◆ Vec [1/2]

◆ Vec [2/2]

Enumeration Type Documentation

◆ CoulombMethod

◆ DiisStrategy

◆ DispersionType

◆ FittingKind

◆ GuessKind

◆ PopulationKind

◆ SpinComponent

◆ SpinorbitalKind

Function Documentation

◆ build_guess()

◆ chelpg_charges()

◆ cosx_nbf_crossover()

◆ expectation() [1/3]

◆ expectation() [2/3]

◆ expectation() [3/3]

◆ from_json() [1/2]

◆ from_json() [2/2]

◆ generate_auto_aux()

◆ get_spinorbital_kind_from_string()

◆ guess_kind_from_string()

◆ guess_kind_name()

◆ guess_kind_names()

◆ is_odd()

◆ matrix_dimensions() [1/2]

◆ matrix_dimensions() [2/2]

◆ merge_atoms()

◆ merge_basis_sets()

◆ merge_molecular_orbitals()

◆ minimal_basis_covers()

◆ mulliken_partition()

◆ pipek_mezey() [1/2]

◆ pipek_mezey() [2/2]

◆ resolve_fitting_basis()

◆ ScopedRangeSeparation()

◆ select_guess()

◆ shellblock_norm()

◆ spinorbital_kind_to_string()

◆ supports_incremental_fock_build()

◆ to_json() [1/2]

◆ to_json() [2/2]

Variable Documentation

◆ is_scf_method_v

◆ OCC_MINIMAL_BASIS

◆ supports_density_fitting_v

◆ supports_point_charges_v