> This page is for NVIDIA NIM for Batched Molecular Dynamics, version 1.0.0.
> For other versions, use one of these documentation indexes:
> - 1.1.0 (Latest) (default): https://docs.nvidia.com/nim/alchemi/alchemi-bmd/1.1.0/llms.txt
> - 1.0.0: https://docs.nvidia.com/nim/alchemi/alchemi-bmd/1.0.0/llms.txt

> For clean Markdown of any page, append .md to the page URL.
> For a complete documentation index, see https://docs.nvidia.com/nim/alchemi/llms.txt.
> For AI client integration (Claude Code, Cursor, etc.), connect to the MCP server at https://docs.nvidia.com/nim/alchemi/_mcp/server.

# Environment Variables

Configure NIM for BMD behavior at container startup using the following environment variables.

## Required Variables

| Variable | Required | Default | Description |
|---|---|---|---|
| `NGC_API_KEY` | Yes (for MACE auto-download) | -- | NGC authentication key. Required for the container to download the bundled MACE model from NGC. |

## Configuration Variables

| Variable | Type | Default | Description |
|---|---|---|---|
| `ALCHEMI_NIM_MODEL_TYPE` | string | `"mace"` | Model type: `mace`, `aimnet2`, or `tensornet`. |
| `ALCHEMI_NIM_MODEL_PATH` | string | null | Path to the model file or directory inside the container. |
| `ALCHEMI_NIM_PBC` | bool | true | Periodic boundary conditions. If true, requests must include `cell`. If false, requests must not include `cell`. |
| `ALCHEMI_NIM_BATCH_SIZE` | int | 0 | Batch size in atoms (0 enables auto-estimation at startup). |
| `ALCHEMI_NIM_BATCH_SIZE_ESTIMATE_DATA` | string | `"omat24"` | Dataset used for auto-estimation: `omat24` (bulk materials), `omol25` (molecules), or `omc25` (molecular crystals). |
| `ALCHEMI_NIM_DFT3_ENABLED` | bool | false | Enable DFT-D3(BJ) dispersion correction. |
| `ALCHEMI_NIM_DFT3_PARAM` | string (JSON) | null | JSON string containing custom DFT-D3(BJ) parameters (for example, `{"s8": 0.3908, "a1": 0.5660, "a2": 3.1280}`). Refer to the [ALCHEMI Toolkit-Ops documentation](https://nvidia.github.io/nvalchemi-toolkit-ops/index.html) for details. |

## Container Runtime Variables

| Variable | Required | Default | Description |
|---|---|---|---|
| `NIM_HTTP_API_PORT` | No | `8000` | HTTP port for the inference API. |
| `NIM_DISABLE_MODEL_DOWNLOAD` | No | false | Whether to automatically download the default MACE model from NGC. |

For launch examples, refer to [Custom Models](/nim/alchemi/alchemi-bmd/1.0.0/custom-models) and
[Quickstart Guide](/nim/alchemi/alchemi-bmd/1.0.0/quickstart-guide).

## Related Topics

- [Configuration](/nim/alchemi/alchemi-bmd/1.0.0/configuration) for configuration options, per-request overrides, and model configuration
- [Supported Models](/nim/alchemi/alchemi-bmd/1.0.0/overview#supported-models) for model sourcing