chem-dft-orca-singlepoint

Files (7)

• SKILL.md
• README.md · example/
• h2o.xyz · example/
• input_structure.xyz · example/
• validate_multicore_orca.py · example/
• validate_orca.py · example/
• run_singlepoint.py · scripts/

SKILL.md (first lines)

# DFT Single-Point Calculation with ORCA

## Goal

Compute the DFT electronic energy and optionally forces (gradients) and/or the Hessian for a given molecular structure with the ORCA quantum chemistry program.
The calculation relies on the SCINE wrapper for automated input generation, output parsing, and error handling, with curated defaults suitable for standard cases.

> [!IMPORTANT]
> This skill is for **standard DFT single-point calculations** on molecular (non-periodic) systems. For advanced methods, multi-reference calculations, or properties not exposed here, use the [advanced ORCA skill](../chem-dft-orca-advanced-calculation/SKILL.md). For geometry optimization, use the [ORCA optimization skill](../chem-dft-orca-optimization/SKILL.md).

## 1. Prerequisites

- **Environment:** `cpu` (commands run through `venv/run cpu ...`), which includes `scine_utilities` (x86_64 only) and `ase`
- **ORCA binary:** The environment variable `ORCA_BINARY_PATH` must point to the ORCA executable
  ```bash
  export ORCA_BINARY_PATH=/path/to/orca
  ```
- **Input structure:** A molecular structure file readable by ASE (`.xyz`, `.cif`, `.mol`, etc.)

## 2. Parameters

| Parameter | Default | Description |
|-----------|---------|-------------|
| `--structure` | (required) | Path to input structure file |
| `--charge` | `0` | Molecular charge |
| `--spin_multiplicity` | `1` | Spin multiplicity (2S+1) |
| `--functional` | `PBE` | DFT functional (e.g. `PBE`, `B3LYP`, `wB97X-V`, `PBE0`) |
| `--basis_set` | `def2-SVP` | Basis set (e.g. `def2-SVP`, `def2-TZVP`, `def2-TZVPP`) |
| `--dispersion` | None | Dispersion correction (e.g. `D3BJ`, `D4`) |
| `--solvation` | None | Implicit solvation model: `CPCM` or `SMD` |
| `--solvent` | None | Solvent name (e.g. `water`, `ethanol`, `dmso`); required if `--solvation` is set |
| `--special_option` | `NOSOSCF` | ORCA special option passed to SCINE calculator. Set to empty string to disable. |
| `--nprocs` | `1` | Number of CPU cores for ORCA |
| `--compute_gradients` | off | Flag to also compute forces |
| `--compute_hessian` | off | Flag to also compute the Hessian matrix |
| `--calculator_settings` | None | Extra SCINE calculator settings as a JSON string (see below) |
| `--output_dir` | auto | Output directory |

## 3. Running a Calculation

### Basic energy calculation

```bash
${CLAUDE_SKILL_DIR}/../../venv/run cpu python ${CLAUDE_SKILL_DIR}/scripts/run_singlepoint.py \
    --structure molecule.xyz \
    --output_dir research/my_project/singlepoint
```

### Energy + forces with a hybrid functional and dispersion

```bash
${CLAUDE_SKILL_DIR}/../../venv/run cpu python ${CLAUDE_SKILL_DIR}/scripts/run_singlepoint.py \
    --structure molecule.xyz \
    --functional B3LYP \
    --basis_set def2-TZVP \
    --dispersion D3BJ \
    --compute_gradients \
    --nprocs 4 \
    --output_dir research/my_project/singlepoint
```

### With implicit solvation

```bash
${CLAUDE_SKILL_DIR}/../../venv/run cpu python ${CLAUDE_SKILL_DIR}/scripts/run_singlepoint.py \
    --structure molecule.xyz \
    --functional PBE0 \
    --basis_set def2-TZVP \
    --solvation CPCM \
    --solvent water \
    --compute_gradients \
    --output_dir research/my_project/singlepoint_solvated
```

### With extra SCINE calculator settings

For settings not exposed as dedicated flags, pass a JSON string via `--calculator_settings`. SCINE is strict about types, so JSON ensures values are passed with the correct type (int, float, string).

```bash
${CLAUDE_SKILL_DIR}/../../venv/run cpu python ${CLAUDE_SKILL_DIR}/scripts/run_singlepoint.py \
    --structure molecule.xyz \
    --functional B3LYP \
    --basis_set def2-TZVP \
    --calculator_settings '{"max_scf_iterations": 128}' \
    --output_dir research/my_project/singlepoint_custom
```

> [!IMPORTANT]
> A popular functional choice is 'wB97M-V' which can only be used with the hack "--functional '' --dispersion '' --special_option wB97M-V"
> This hack will work for any functional choice that includes hyphens

### Hessian calculation

```bash
${CLAUDE_SKILL_DIR}/../../venv/run cpu python ${CLAUDE_SKILL_DIR}/scripts/run_singlepoint.py \
    --structure molecule.xyz \
    --functional B3LYP \
    --basis_set def2-TZVP \
    --dispersion D3BJ \
    --compute_gradients \
    --compute_hessian \
    --charge 0 \
    --spin_multiplicity 1 \
    --nprocs 8 \
    --output_dir research/my_project/singlepoint_full
```

### Beyond DFT calculation

ORCA also supports post-HF methods useful for reference calculations, such as local coupled cluster DLPNO-CCSD(T).
This is also available through this skill.

```bash
${CLAUDE_SKILL_DIR}/../../venv/run cpu python ${CLAUDE_SKILL_DIR}/scripts/run_singlepoint.py \
    --structure molecule.xyz \
    --functional DLPNO-CCSD(T) \
    --basis_set def2-TZVP \
    --charge 0 \
    --spin_multiplicity 1 \

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