# ThirdOrder

**Repository Path**: fenggo/ThirdOrder

## Basic Information

- **Project Name**: ThirdOrder
- **Description**: thirdorder, help compute anharmonic IFCs from minimal sets of displacements with GULP and LAMMPS.
- **Primary Language**: Python
- **License**: GPL-3.0
- **Default Branch**: master
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 0
- **Forks**: 0
- **Created**: 2023-01-09
- **Last Updated**: 2024-07-10

## Categories & Tags

**Categories**: Uncategorized

**Tags**: None

## README

# ThirdOrder

#### Introduction
A Modified Third-Order Version to Work with GULP and LAMMPS, for the comptation the force constant with the machine learning potential.

thirdorder, help compute anharmonic IFCs from minimal sets of displacements

Forked from: https://bitbucket.org/sousaw/thirdorder/



#### Installation

python setup install/build --user

####  Compute 3rd FC with thirdorder and GULP with ReaxFF-nn Machine learning potential

Any invocation of thirdorder_gulp.py requires a POSCAR.0 file with a description of the unit cell to be present in the current directory. The script uses no other configuration files, and takes exactly five mandatory command-line arguments:

```bash
./thirdorder_gulp.py sow|reap na nb nc cutoff[nm/-integer]
```

The first argument must be either "sow" or "reap", and chooses the operation to be performed (displacement /generation or IFC matrix reconstruction). The next three must be positive integers, and specify the dimensions of the supercell to be created. Finally, the "cutoff" parameter decides on a force cutoff distance. Interactions between atoms spaced further than this parameter are neglected. If cutoff is a positive real number, it is interpreted as a distance in nm; on the other hand, if it is a negative integer -n, the maximum distance among n-th neighbors in the supercell is automatically determined and the cutoff distance is set accordingly.

* 1. Generating the displacement files using the command bellow:
```bash
./thirdorder_gulp.py sow 1 1 4 1
```
* 2. Compute the force constant matrix
```bash
./thirdorder_gulp.py reap 1 1 4 1
```
where "1 1 4" is super cell, and the last number "1" is cutoff for interactions: 1 nm.

The force constant file is FORCE_CONSTANT_3RD

* 3. Using ShengBTE to compute the thermal conductivity. 
Modify the content of CONTROL file, and submit compute tasks using command: 

```bash
nohup mpirun -n 8 ./ShengBTE > sheng.out 2>& 1 & 
```