Know the method.
Know its scope.

Hartree-Fock: RHF, UHF, ROHF

Analytic nuclear gradients, analytic and finite-difference Hessians, direct and in-core Fock builds.

Kohn-Sham DFT: RKS, UKS, ROKS

Over 500 libxc functionals: LDA, GGA, meta-GGA, global and range-separated hybrids, VV10 and double hybrids. Range-separated and VV10 gradients fall back to finite differences and say so in the output.

SKALA-1.1 neural exchange-correlation

Optional PyTorch checkpoint provider behind [skala], with molecular RKS/UKS/ROKS and selected periodic AO-grid routes. Fixed-geometry energies only; derivatives and response fail closed.

Dispersion: D3(BJ), D4

Native D3(BJ), plus D4 through the optional dftd4 package. The native D4 backend has restricted element coverage; check the documented backend before selecting it.

Composite 3c methods (HF-3c, PBEh-3c, B97-3c, ...)

Tuned basis plus dispersion, geometric counterpoise and short-range corrections in one keyword. Calibrated on molecules; the periodic flavours need recalibration.

MANTA integral engine with independent Coulomb and exchange builds

An opt-in second integral engine for molecules and crystals: exact, RI, multipole (BUPO) or RI-BUPO Coulomb and exact or RI exchange, with an explicit resource budget and the executed provider recorded. The exact build matches libint to 1e-10 Ha; libint stays the default.

Density fitting: RIJK, RIJCOSX

RIJCOSX energies within 0.3 mHa of ORCA on glycine/def2-TZVP. The RIJCOSX gradient carries the documented grid-response residual.

Effective core potentials

libecpint with the Stuttgart-Koeln MDF and LANL2DZ libraries plus per-basis sidecars. ECP-aware analytic gradients on all four molecular drivers.

Implicit solvation: CPCM, COSMO

Conductor-like screening with analytic gradients for HF and DFT. COSMO-RS thermodynamics on the same surface is experimental; solvent with correlated methods is gated.

Basis sets and basis optimisation

Bundled Gaussian sets including the solid-state pob family, on-demand Basis Set Exchange rendering, and molecular/crystal basis-optimization recipes with provenance-aware saving in vibe-basis.

MP2 family: MP2, RI-MP2, SCS/SOS-MP2, UMP2, ROHF-MP2

Validated to 1e-9 Ha against PySCF. The dense routes are accuracy references at small-molecule size, not production-size solvers.

Double hybrids: B2PLYP, DSD-PBEP86, revDSD-PBEP86-D4

Hybrid SCF plus scaled RI-MP2 in one call.

Coupled cluster: CCSD, CCSD(T), UCCSD(T), ROHF-CCSD(T), FNO

Small-molecule accuracy reference validated to microhartree against PySCF and ORCA. The dense CC iteration remains a production-size memory gate.

CC2, CC3, CCSDT, QCISD(T), CEPA(n), LCCD, CCD, A-CCSD(T)

Energy-only benchmark implementations pinned against ORCA. CC3 and CCSDT use a dense determinant representation that grows combinatorially.

DLPNO-MP2, DLPNO-CCSD(T), open-shell DLPNO-UMP2 and DLPNO-UCCSD(T)

Local correlation with pair natural orbitals. At the shipped defaults the mean absolute error against canonical CCSD(T) is 0.38 kcal/mol on 17 molecules up to C10H22 (0.19 with TightPNO); state the thresholds when you publish.

CISD

Fixed-space variational singles and doubles CI with determinant-space guards.

Multireference: CASCI, CASSCF, IC-CASPT2, NEVPT2, MRCI

Multi-root CASCI and state-averaged CASSCF. The state-specific closed-shell CASSCF analytic gradient is finite-difference tight to about 1e-7; PT2 gradients are analytic only in a narrow envelope and finite-difference otherwise.

Determinant solvers: full CI, selected CI (CIPSI), v2RDM

Exact and near-exact references on a chosen active space with the proper frozen-core dressing; the v2RDM solver has no Q/G semidefinite feedback yet.

DMRG

A toy matrix-product-state solver cross-checked against full CI; it refuses more than 6 spatial orbitals (12 spin orbitals).

Transcorrelated CI

Similarity-transformed Hamiltonian with a research-grade correlator fed to selected CI.

Green's function: GF2, OVGF

Quasiparticle ionisation potentials and electron affinities, including renormalised GF2 and an open-shell propagator.

TDDFT: Casida and Tamm-Dancoff, NTOs, UV/Vis spectra

RHF, RKS, UHF and UKS references; ROHF supports a restricted TDA excitation space. Excited-state gradients use finite differences on the closed-shell RHF/CIS surface only; range-separated kernels and ROKS response are refused.

MSINDO (INDO and NDDO)

INDO energy for H to Xe with restricted and unrestricted molecular routes; NDDO covers closed-shell H, Li to F and Na to Cl. Gradients, dynamics, solvation and excited-state workflows have their own method and element limits.

DFTB0, SCC-DFTB

Screening and preoptimisation with in-house parameters. No DFTB+ parity; absolute energies are not claimable while the repulsive is a placeholder.

GFN2-xTB

Molecular Hamiltonian, analytic gradients and Gamma-periodic derivatives are implemented; external xtb parity and periodic AES electrostatics remain production gates.

PM6

Molecular development route. MOPAC heat-of-formation parity is open; periodic PM6 is experimental.

OM1, OM2, OM3

Retirement target: still executable as molecular prescreening, no periodic target, scheduled for removal from the public portfolio.

PM7

Recognised spelling that fails closed. The feathered electrostatics are not implemented and PM7 has never been executable in any release.

SECCM: semiempirical cyclic cluster model

MSINDO, DFTB, GFN2-xTB and PM6 on a finite cyclic cluster in one, two and three dimensions, with opt-in Madelung embedding.

MACE machine-learned interatomic potential

An external pre-trained model behind the optional [mace] extra, attributed as such. vibe-qc drives its forward pass for energies, forces, optimisation and NEB; it is not a vibe-qc electronic-structure method.

GDF: Gaussian density fitting, Gamma and multi-k, slabs and crystals

Microhartree parity with PySCF on LiH and MgO, mixed density fitting for dense crystals, closed-shell slab analytic gradients. A 1-D wire is refused and runs as a 3-D cell with transverse vacuum.

GPW: Gaussian plane waves

Serial route with Gamma RHF/UHF/RKS/UKS, multi-k pure DFT, Gamma analytic gradients and DFT+U, production within that envelope. The run description carries an experimental tag and the grid build warns once while the surrounding family (GAPW defaults, multi-k hybrids) is completed.

GAPW: all-electron augmentation

Not the automatic default. Molecular-limit Gamma HF and block-construction DFT ship; compact-crystal augmentation validation is pending.

BIPOLE: exact Ewald J split

Gamma and multi-k RHF/UHF/RKS/UKS with finite-difference forces and fixed-cell relaxation. Analytic gradients are a preview; the quartet multipole far field is gated.

Periodic RIJCOSX

RI-J from the native GDF loop plus periodic chain-of-spheres exchange on true multi-k meshes.

2D slab Ewald

Vacuum-free two-dimensional Ewald for RHF, RKS and UKS; selected automatically for every slab.

DLPNO-CCSD(T) on crystals

run_periodic_job(method="dlpno-ccsd(t)") on an RHF or UHF GDF reference at Gamma or on a k mesh folded to the Born-von Karman supercell, with the molecular local-correlation engine. Full domains reproduce PySCF KRCCSD(T); accuracy at the shipped thresholds on real crystals is not yet measured.

Symmetry-reduced exact exchange on k meshes

symmetry_reduce_k=True builds exchange only at the irreducible-wedge representatives and transports it over each star; energies equal the full mesh to roundoff.

Periodic ROHF and ROKS

GDF supports ROHF at Gamma and full multi-k in 3D; GPW supports Gamma ROHF and Gamma/multi-k pure-DFT ROKS. GDF ROKS, gradients, electronic smearing and slabs remain closed.

Metals: Fermi-Dirac, Methfessel-Paxton and Marzari-Vanderbilt smearing, density mixers

Anderson, Broyden and Kerker mixing with an automatic k-point and smearing recommender.

DFT+U

Dudarev correction on GPW: Gamma RHF/RKS/UHF/UKS and multi-k RKS within the documented projector and occupation scope.

Band structure, density of states, PDOS, fat bands

k-path sampling, Gaussian-broadened and Mulliken-projected densities of states, projected band weights.

COOP and COHP bonding analysis

Energy-resolved crystal orbital overlap and Hamilton populations on the GDF routes, computed with the analysed spin Hamiltonian; skipped with a stated reason on BIPOLE, AICCM and external-XC routes.

Periodic Mayer bond orders and QTAIM topology

k-space Mayer indices; critical-point search and bond-path tracing on periodic and molecular densities.

Gamma-point phonons

Finite displacement on the analytic GAPW force at the Gamma point only; multi-k phonons are not wired.

Stress and variable-cell relaxation

Finite-difference fixed-density stress on GPW/GAPW; semiempirical stress is route-specific, including analytic Gamma GFN2-xTB stress. Ab initio variable-cell relaxation remains closed; selected full-k semiempirical routes support it.

Surface embedding (Green's function)

Embedded-surface calculator on a validated 3D Gaussian foundation; thick-slab parity is pending, so absolute energies are qualitative.

AICCM: ab initio cyclic cluster model (real-gamma, neutral-bloch, four-center, chi)

Two independent research lines, Gamma-CCM and chi-CCM, from HF through DLPNO correlation on a finite Born-von Karman torus. Every driver warns and no cross-approach result is reportable yet.

MPI grid overlay for GPW

Distributed Hartree build behind the [mpi] extra, pending validation on a real multi-rank run.

Geometry optimisation, relaxed scans, intrinsic reaction coordinates

ASE and native optimisers; molecular IRC by mass-weighted damped steepest descent. Periodic IRC fails closed.

Nudged elastic band

Climbing-image NEB through ASE on any calculator with forces.

Molecular dynamics, metadynamics, conical intersections

Velocity-Verlet, Berendsen and Nose-Hoover dynamics on any surface with forces; well-tempered metadynamics on the same driver; penalty-function MECI optimisation from two tracked states.

Hessians, frequencies, IR intensities, thermochemistry

Analytic HF and supported KS Hessians, with finite differences on documented derivative routes. Meta-GGA analytic Hessians, incomplete gradients and basis-free semiempirical/MLIP routes have explicit limits; thermochemistry requires supported frequencies.

Static polarizability

Coupled-perturbed HF for closed shells.

Charges and bond orders: Mulliken, Loewdin, Hirshfeld, IAO, Mayer, Wiberg, delocalization index

Population and bond analysis where the executed method provides the required density and basis data; IAO/IBO analysis and its three bonding criteria have documented scope.

Orbital entanglement measures

Single-orbital entropies, mutual information and entanglement bond orders on a correlated reduced density matrix; the convenience density wrapper is an approximation.

Energy decomposition analysis

LMO-EDA and Kitaura-Morokuma terms for two closed-shell Hartree-Fock fragments in the dimer basis, summing to the interaction energy. Kohn-Sham, open-shell and ECP inputs are refused; there is no run_job keyword yet.

NPA charges

Raises NotImplementedError until occupancy-weighted natural atomic orbitals are implemented. Population sidecars record NPA as unavailable.

Provisional NBO search

Exploratory Python orbital classification and donor-acceptor analysis are implemented; this is not a complete NAO/NBO construction.

Equation-of-state fits and atomisation energies

Third-order Birch-Murnaghan fits with quality gates; atomisation energies against free-atom references at the same level.

Volumetric and orbital export: cube, XSF, BXSF, Molden

Densities and orbitals for molecules and crystals; Fermi surfaces for XCrySDen.

QVF archives, TREXIO, QCSchema, ASE and structure fetchers

One QVF archive per run for vibe-viewer; TREXIO and QCSchema interchange; CIF, POSCAR and extended XYZ readers with symmetrisation; vqfetch for OPTIMADE, Materials Project, COD and NIST data.