## Relaxation get started and input examples

The relaxation of a structure should be carried out before calculating all other properties.

First, we need input parameter file and we name it `relax.json` here. All the relaxation calculations should be taken either by `VASP`, `ABACUS`, or `LAMMPS`. Here are two input examples for `VASP` and `LAMMPS` respectively.

An example of the input file for relaxation by VASP:

```json
{
  "structures": [
    "confs/std-*"
  ],
  "interaction": {
    "type": "vasp",
    "incar": "vasp_input/INCAR",
    "potcar_prefix": "vasp_input",
    "potcars": {
      "Al": "POTCAR.al"
    }
  },
  "relaxation": {
    "cal_type": "relaxation",
    "cal_setting": {
      "relax_pos": true,
      "relax_shape": true,
      "relax_vol": true,
      "ediff": 1e-06,
      "ediffg": -0.01,
      "encut": 650,
      "kspacing": 0.1,
      "kgamma": false
    }
  }
}
```

| Key words       | data structure | example                  | description                                                 |
| --------------- | -------------- | ------------------------ | ----------------------------------------------------------- |
| **structures**  | List of String | ["confs/std-\*"]         | path of different structures                                |
| **interaction** | Dict           | See above                | description of the task type and atomic interaction         |
| **type**        | String         | "vasp"                   | task type                                                   |
| **incar**       | String         | "vasp_input/INCAR"       | path for INCAR file in vasp                                 |
| potcar_prefix   | String         | "vasp_input"             | prefix of path for POTCAR file in vasp, default = ""        |
| **potcars**     | Dict           | {"Al": "POTCAR.al"}      | key is element type and value is potcar name                |
| **relaxation**  | Dict           | See above                | calculation type and setting for relaxation                 |
| cal_type        | String         | "relaxation" or "static" | calculation type                                            |
| cal_setting     | Dict           | See above                | calculation setting                                         |
| relax_pos       | Boolean        | true                     | relax atomic position or not, default = true for relaxation |
| relax_shape     | Boolean        | true                     | relax box shape or not, default = true for relaxation       |
| relax_vol       | Boolean        | true                     | relax box volume or not, default = true for relaxation      |
| ediff           | Float          | 1e-6                     | set `EDIFF` parameter in INCAR files                        |
| ediffg          | Float          | -0.01                    | set `EDIFFG` parameter in INCAR files                       |
| encut           | Int            | 650                      | set `encut` parameter in INCAR files                        |
| kspacing        | Float          | 0.1                      | set `KSPACING` parameter in INCAR files                     |
| kgamma          | Boolean        | false                    | set `KGAMMA` parameter in INCAR files                       |

An example of the input file for relaxation by LAMMPS:

```json
{
  "structures": [
    "confs/std-*"
  ],
  "interaction": {
    "type": "deepmd",
    "model": "frozen_model.pb",
    "in_lammps": "lammps_input/in.lammps",
    "type_map": {
      "Al": 0
    }
  },
  "relaxation": {
    "cal_setting": {
      "etol": 0,
      "ftol": 1e-10,
      "maxiter": 5000,
      "maximal": 500000
    }
  }
}
```

**Other key words different from vasp:**

| Key words    | data structure           | example                  | description                                                                          |
| ------------ | ------------------------ | ------------------------ | ------------------------------------------------------------------------------------ |
| **model**    | String or List of String | "frozen_model.pb"        | model file for atomic interaction                                                    |
| in_lammps    | String                   | "lammps_input/in.lammps" | input file for lammps commands                                                       |
| **type_map** | Dict                     | {"Al": 0}                | key is element type and value is type number. DP starts from 0, others starts from 1 |
| etol         | Float                    | 0                        | stopping tolerance for energy                                                        |
| ftol         | Float                    | 1e-10                    | stopping tolerance for force                                                         |
| maxiter      | Int                      | 5000                     | max iterations of minimizer                                                          |
| maxeval      | Int                      | 500000                   | max number of force/energy evaluations                                               |

For LAMMPS relaxation and all the property calculations, **package will help to generate `in.lammps` file for user automatically** according to the property type. We can also make the final changes in the `minimize` setting (`minimize etol ftol maxiter maxeval`) in `in.lammps`. In addition, users can apply the input file for lammps commands in the `interaction` part. For further information of the LAMMPS relaxation, we refer users to [minimize command](https://lammps.sandia.gov/doc/minimize.html).