Manual phonon finite differences

Description

Introducing a manual page for the finite difference phonon calculations. Also adds some in-code documentation and minor code cleaning.

News snippet

Introducing a manual page for the finite difference phonon calculations.

Checklist

• I have checked that my code follows the Octopus coding standards
• I have added tests for all the new features added in this request.

changed milestone to %15.0

added Documentation Refactoring labels

assigned to @nicolastd

added 1 commit

• d6f4833c - Update the test as one header line was added.

Compare with previous version

@martin.lueders This branch seems to be ready to be merge. Do you think you could review it?

approved this merge request

Looks good.

merged

mentioned in commit f2d849ad

added in Changelog label