https://github.com/zhubonan/castep-linear-response-u

Example for calculating U value in DFT+U using CASTEP with the ab inito linear response method
https://github.com/zhubonan/castep-linear-response-u

Last synced: about 2 months ago
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Example for calculating U value in DFT+U using CASTEP with the ab inito linear response method

• Host: GitHub
• URL: https://github.com/zhubonan/castep-linear-response-u
• Owner: zhubonan
• Created: 2020-11-04T23:44:34.000Z (over 4 years ago)
• Default Branch: master
• Last Pushed: 2020-11-04T23:46:45.000Z (over 4 years ago)
• Last Synced: 2025-03-30T10:12:35.825Z (3 months ago)
• Language: Jupyter Notebook
• Size: 726 KB
• Stars: 2
• Watchers: 1
• Forks: 3
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

        
# Computing ab inito U value using the linear response method with CASTEP

## How to run

1. Have CASTEP compiled and `castep.mpi` in the `$PATH`

2. `base script.sh`

3. Run this notebook or `python post-process.py`

![Results for the toy system](https://raw.githubusercontent.com/zhubonan/castep-linear-response-u/master/response.png)

## How it works

Adjust the `HUBBARD_ALPHA` value and record the initial and final occupations of the Mn d levels when continuing from the unperturbed run (`base_calc`).

The value of U is extracted using the gradient of the two response curves.

The example in  http://hjkgrp.mit.edu/content/calculating-hubbard-u is reused here and the same methodology is followed.  

The more `self-consistent` U can be computed by repeating the procedure with different input value for the U.

Reference: 

>  Cococcioni, M.; de Gironcoli, S. Linear Response Approach to the Calculation of the Effective Interaction Parameters in the LDA+U Method. Phys. Rev. B 2005, 71 (3), 035105. https://doi.org/10.1103/PhysRevB.71.035105.

DISCLAIMER: Use at your own risk. Please raise an issue if you think the method here is not correct due to implementation details.