Docs: we need a doc to introduce fixed-potential method

[WHUweiqingzhou]

Details

Call for a doc to introduce the fixed-potential method

Have you read the online manual http://abacus.deepmodeling.com/en/latest/

• [X] Yes, I have read the online manual.

Task list for Issue attackers (only for developers)

• [ ] Identify the specific section of the documentation with the issue.
• [ ] Investigate the issue and determine the root cause.
• [ ] Research best practices and potential solutions for the identified issue.
• [ ] Update the documentation to address the issue, following the suggested improvement.
• [ ] Ensure the updated documentation adheres to the project's documentation standards.
• [ ] Test the updated documentation to ensure it is clear and accurate.
• [ ] Review and incorporate any relevant feedback from users or developers.
• [ ] Publish the updated documentation and notify the issue reporter.