Environment Variables

Variable	Description
`OPENQUANTUM_SCRATCH`	Directory for temporary files. Defaults to the OS temporary directory (`/tmp` on Linux/macOS, `%TEMP%` on Windows) when not set.
`OPENQUANTUM_BASIS_PATH`	Override the search path for external basis-set files (GBS, BAS, or JSON format).

Basis Search Path

When resolving an external or custom basis set (not built into the binary), OpenQuantum searches directories in this order:

Directory from the OPENQUANTUM_BASIS_PATH environment variable
basis/ subdirectory next to the running executable
basis/ subdirectory in the current working directory
Source-tree fallback: crates/basis/src/data/ (development only)

Files are named <basis_name_lowercase>.<ext> with the following extensions:

Extension	Format
`.gbs`	Gaussian GBS format
`.bas`	Orca export format (`orca_exportbasis`)
`.json`	JSON basis format

HPC Example

# SLURM job script
#SBATCH --job-name=oquantum
#SBATCH --ntasks=1

export OPENQUANTUM_SCRATCH=/scratch/$USER/$SLURM_JOB_ID
mkdir -p $OPENQUANTUM_SCRATCH

oquantum myjob.inp

The scratch directory is always printed at the start of each run:

  Scratch directory: /scratch/user/12345345

Debug Environment Variables

Variable	Description
`OPENQ_DIIS_TRACE`	Set to `1` to print concise DIIS attempt/accept/fallback trace lines for debugging DIIS behavior
`OPENQ_BFGS_TRACE`	Set to `1` to print BFGS line-search accept/reject/reset behavior