Module scf 

Core SCF (Self-Consistent Field) engine.

This module provides shared, production-quality implementations of the fundamental SCF building blocks used across the library:

• DIIS — Pulay’s Direct Inversion in the Iterative Subspace convergence accelerator
• Orthogonalization — Löwdin S^{-1/2} symmetric orthogonalization
• Density matrix — RHF density matrix construction from MO coefficients
• Energy — Electronic, nuclear repulsion, and total energy evaluation
• Mulliken — Mulliken and Löwdin population analysis
• Fock matrix — Modular Fock matrix construction (HF and DFTB)
• Two-electron integrals — (μν|λσ) ERI with sequential and parallel paths
• Core matrices — Grouped one-electron matrices (S, T, V, H⁰)
• Basis set — STO-3G contracted Gaussian basis functions
• Gaussian integrals — Primitive integral evaluation (Obara-Saika)
• Overlap matrix — S_μν overlap integrals
• Kinetic matrix — T_μν kinetic energy integrals
• Nuclear matrix — V_μν nuclear attraction integrals

Modules

basis

STO-3G minimal basis set with contracted Gaussian primitives.

constants

Physical and mathematical constants for quantum chemistry.

core_matrices

Core one-electron matrices: S, T, V, and H⁰ = T + V.

density_matrix

Density matrix construction from MO coefficients.

diis

Direct Inversion in Iterative Subspace (DIIS) convergence accelerator.

energy

Energy evaluation from density and Fock matrices.

extended_basis

Extended basis set library: 3-21G and 6-31G.

fock_matrix

Fock matrix construction.

gaussian_integrals

Primitive Gaussian integral evaluation using Obara-Saika recursion.

gradients

Analytical and numerical nuclear gradients ∂E/∂R.

kinetic_matrix

Kinetic energy matrix T_μν construction.

mulliken

Mulliken and Löwdin population analysis.

nuclear_matrix

Nuclear attraction matrix V_μν construction.

orthogonalization

Löwdin and canonical orthogonalization of the overlap matrix.

overlap_matrix

Overlap matrix S_μν construction from contracted Gaussian basis.

scf_loop

Main SCF iteration driver.

two_electron

Two-electron repulsion integrals (μν|λσ).

types

Shared types for SCF calculations.

validation

Validation utilities for comparing CPU and GPU results.