Input File Format

OpenMECP input files use a custom section-based format. Sections are delimited by a *SECTION_NAME opening marker and a bare * closing marker. Keywords are specified as key = value pairs outside sections (or they can appear after the geometry section).

File Layout

*GEOM
  <Cartesian coordinates>
*

*TAIL_A
  <extra QM keywords for state A>
*

*TAIL_B
  <extra QM keywords for state B>
*

keyword1 = value1
keyword2 = value2
...

Section names are case-insensitive (*GEOM, *geom, and *Geom are all equivalent).

Section Reference

SectionRequiredPurpose
*GEOMYesInitial geometry in Cartesian coordinates
*TAIL_ARecommendedExtra QM input for state A
*TAIL_BRecommendedExtra QM input for state B
*CONSTRNoGeometric constraints and PES scan specs
*LST_ANoTarget geometry for LST interpolation (state A)
*LST_BNoTarget geometry for LST interpolation (state B)

Keywords

All parameters controlling the run are specified as key = value pairs after the geometry section. See the Keywords Reference for the full list.

Minimum required keywords:

program  = gaussian    # or orca
method   = B3LYP/6-31G*
nprocs   = 4
mem      = 4GB
charge   = 0
mult_a   = 1
mult_b   = 3