Some files can be removed in DeePKS.

[ErjieWu]

Describe the Code Quality Issue

The deepks_hmat.cpp contains two functions called collect_h_mat() and check_h_mat(). The first one is used to convert a matrix from vector type to matrix type (and collect data from different process). But this is used later only for output and maybe it can be simplified. The second function is not used anywhere in the code. So this file can be removed.

Also, files in doxygen/ and sphinx/ directories are not used now and can be safely removed.

Additional Context

No response

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.