[guess]

The [guess] section controls initial orbitals, JSON restart files, and manual MO swaps. Most users can start with the default Huckel guess.

Minimal Example

[guess]
type=huckel

Keywords

type

Field	Value
Type	string
Default	huckel
Values	huckel, modhuckel, hcore, json, auto, sap, minao
Used by	initial density/orbital construction

Selects the initial guess mode.

Value	Meaning
huckel	Native extended-Huckel style guess.
modhuckel	Modified Huckel guess.
hcore	Core-Hamiltonian guess.
json	Read orbitals and molecular data from a JSON restart file.
auto	Read file if it exists; otherwise fall back to Huckel.
sap	Superposition-of-atomic-potentials guess.
minao	Projected minimal-basis density guess.

Use json for exact restarts and auto for workflows that may or may not have a previous restart file.

file

Field	Value
Type	string
Default	empty
Used by	type=json, type=auto

Path to a JSON restart file. With type=json, the file must exist. With type=auto, OpenQP uses it when present and otherwise computes a fresh guess.

file2

Field	Value
Type	string
Default	empty
Used by	NACME and previous-step workflows

Path to a second JSON restart file. NACME can use file2 for previous-step information. If it is omitted, NACME can instead use [input] system2.

save_mol

Field	Value
Type	boolean
Default	False
Used by	restart/debug workflows

Requests saving molecular data for later restart or inspection. Leave it off for ordinary production inputs unless a workflow explicitly needs a JSON restart.

continue_geom

Field	Value
Type	boolean
Default	False
Used by	JSON restart geometry

When true, reuses geometry from the JSON restart file. The input checker warns if continue_geom=true is set without type=json.

swapmo

Field	Value
Type	comma-separated integer list
Default	empty
Used by	manual orbital reordering before SCF

Swaps molecular orbitals in pairs. The list must contain an even number of indices:

[guess]
swapmo=2,7,8,21

This swaps 2 with 7 and 8 with 21. Use it only when you know the target orbital ordering.