OpenRSP: open-ended response theory

Code

• Now requires Fortran 2008
• Rewrote linked list functionality for caching to instead use (reallocating) arrays
• "Number of components" marker in rsp_tensor output file now written as 'NUM_COMPONENTS' instead of 'NUM COMPONENTS'
• Significantly decreased usage of array constructors in function/subroutine arguments
• Fixed various memory leak/out-of-bounds errors that sometimes would happen
• OpenRSP now looks for available file units before choosing one to use
• Disabled internal memory limit and memory bookkeeping, may be reinstated later
• If a response tensor is large, then if it's printed at the debugging print level, it's broken down into smaller chunks
• Added stops for various currently unsupported residue calculation setups
• Fixed a bug concerning testing of perturbation frequencies against excitation energy for residue calculations
• Removed some unused residue-related routines
• Calculation setup errors encountered in wrapper routines now cause exit, not just warning and then continuing

Project

• Added contribution guide and authorship process guide
• Updated pull request template to solicit agreement to contribution terms
• Various changes to documentation

Known issues

• Now compiles and runs with most compilers but still problems with some Intel/2018 and Intel/2019 setups
• The "excitation" perturbation in a single residue calculation is now given the label EX1 in the rsp_tensor file; however, its current implementation still results in triplication of the calculation result data due to being treated as having three components when in fact it has got only one
• Does not yet support calculations involving perturbations that are both non-static and change the basis set (the foremost example of such a perturbation is the magnetic dipole perturbation with London atomic orbitals)