AOM Formats¶
The Atomic Overlap Matrix (AOM) stores the integrals \(S^A_{ij} = \langle \phi_i | \hat{w}_A | \phi_j \rangle\) of each molecular orbital pair \(i,j\) over the basin of atom \(A\). These integrals encode the partitioning of space into molecular fragments.
The source and format of the AOM is selected by ioverlap (Record 1).
ioverlap = 0 — PROMOLDEN format or fuzzy partition¶
When filedat is a filename, edf reads an AOM file produced by PROMOLDEN (the standard case for QTAIM basins). The PROMOLDEN format is a plain-text table with one block per atom.
When filedat is a keyword (mulliken, lowdin, mindef, etc.), edf computes the AOM internally using a fuzzy-atom weighting scheme. See Input Format — Record 2 for the full list of keywords.
ioverlap = 1 — PROAIM format¶
AOM from the PROAIM program (QTAIM basins). PROAIM is an older topological analysis code; its AOM format differs from PROMOLDEN in the header and ordering of matrix elements. edf detects and parses this format automatically when ioverlap = 1.
ioverlap = 2 — TOPMOD, ELF basins¶
AOM from TOPMOD using ELF (Electron Localization Function) basins. ELF basins divide space according to the topology of the electron localization function rather than the electron density.
ioverlap = 3 — TOPMOD, QTAIM basins¶
AOM from TOPMOD using QTAIM (Quantum Theory of Atoms in Molecules) basins, i.e., the gradient-field basins of the electron density \(\rho\). Same program as ioverlap = 2 but with different basin topology.
ioverlap = 4 — AIMALL format¶
AOM from AIMALL (QTAIM basins). AIMALL produces a dedicated AOM output file; select this value when the .aom file was generated with AIMALL rather than PROMOLDEN or PROAIM.
ioverlap = -1 — Complex AOM (edfx)¶
A complex Atomic Overlap Matrix. Control passes immediately to edfx.f, which has its own input grammar. Consult the edfx.f source file for the format of additional input records in this mode.
ioverlap = -2 — Complex AOM (edfcrit)¶
A complex Atomic Overlap Matrix sourced from critic2. Control passes to edfcrit.f. Consult edfcrit.f for the additional input expected in this mode.
ioverlap = -11 — Single-determinant fast path¶
For single-determinant wavefunctions (RHF, ROHF, UHF). After reading the AOM, control passes to edfstd.f, which uses an optimized closed-shell algorithm. Additional keywords specific to edfstd.f may follow. Consult edfstd.f for its input grammar.
AOM normalization check¶
For all formats, edf verifies that the AOM satisfies the idempotency sum rule:
If any diagonal deviation exceeds TOLAOM (default 0.01), edf stops with an error. Use AOMNORM to fix a poorly normalized AOM (see Keywords — Basic).
Summary table¶
ioverlap |
Source | Basin type |
|---|---|---|
0 |
PROMOLDEN file or fuzzy keyword | QTAIM or fuzzy |
1 |
PROAIM | QTAIM |
2 |
TOPMOD | ELF |
3 |
TOPMOD | QTAIM |
4 |
AIMALL | QTAIM |
-1 |
Complex AOM → edfx.f |
— |
-2 |
Complex AOM from critic2 → edfcrit.f |
— |
-11 |
Any AOM → edfstd.f fast path |
Single-det only |