determineKMatSize Function

    function determineKMatSize() result(kMatSize)
        implicit none
        integer(int64) :: kMatSize
        integer :: nBI

        nBI = numBasisIndices(nBasis)
! kmat has the same access pattern as umat, so use UMatInd as indexing function
! the index of the largest element
        kMatSize = UMatInd(nBI, nBI, nBI, nBI)
    end function determineKMatSize