The need to change the unit of decay gradient in deltaspin calculation

[hongriTianqi]

Describe the Code Quality Issue

The output decay gradient now is in unit of uB^2/Ry, which is different as set in input file (uB^2/eV). This may cause bad user-friendliness. So I suggest to change the output unit of decay gradient in deltaspin calculation to uB^2/eV.

Additional Context

The output decay gradient now is in unit of uB^2/Ry, which is different as set in input file (uB^2/eV). This may cause bad user-friendliness. So I suggest to change the output unit of decay gradient in deltaspin calculation to uB^2/eV.

Task list for Issue attackers (only for developers)

• Identify the specific code file or section with the code quality issue.
• Investigate the issue and determine the root cause.
• Research best practices and potential solutions for the identified issue.
• Refactor the code to improve code quality, following the suggested solution.
• Ensure the refactored code adheres to the project's coding standards.
• Test the refactored code to ensure it functions as expected.
• Update any relevant documentation, if necessary.
• Submit a pull request with the refactored code and a description of the changes made.