refactoring of DFT-D3 code

- remove zero damping backend (no users here)
- purge copyc6 in favor of ase-d3 kind implementation

meson.build

@@ -148,7 +148,6 @@ xtb_srcs += 'xtb/scanparam.f90'
 xtb_srcs += 'xtb/splitparam.f90'
 xtb_srcs += 'xtb/symparam.f90'
 xtb_srcs += 'xtb/fixparam.f90'
-xtb_srcs += 'xtb/d3param.f90'
 xtb_srcs += 'xtb/aoparam.f90'
 xtb_srcs += 'xtb/setparam.f90'
 
@@ -182,7 +181,7 @@ xtb_srcs += 'xtb/tbmod_file_utils.f90'
 
 # parameters
 xtb_srcs += 'xtb/gfn_paramset.f90'
-xtb_srcs += 'xtb/copyc6.f'
+xtb_srcs += 'xtb/dftd3_parameters.f90'
 xtb_srcs += 'xtb/setwll.f'
 xtb_srcs += 'xtb/charge_model.f90'
 

xtb/asym.f90

@@ -73,3 +73,27 @@ pure elemental subroutine upper10(as)
       as(i:i)=char(j)
    enddo
 end subroutine upper10
+
+pure elemental function esym(i)
+   integer,intent(in) :: i
+   character(len=2) :: esym
+   character(len=2),parameter :: elemnt(118) = (/ &
+   & 'h ','he', &
+   & 'li','be','b ','c ','n ','o ','f ','ne', &
+   & 'na','mg','al','si','p ','s ','cl','ar', &
+   & 'k ','ca', &
+   & 'sc','ti','v ','cr','mn','fe','co','ni','cu','zn', &
+   &           'ga','ge','as','se','br','kr', &
+   & 'rb','sr', &
+   & 'y ','zr','nb','mo','tc','ru','rh','pd','ag','cd', &
+   &           'in','sn','sb','te','i ','xe', &
+   & 'cs','ba','la', &
+   & 'ce','pr','nd','pm','sm','eu','gd','tb','dy','ho','er','tm','yb', &
+   & 'lu','hf','ta','w ','re','os','ir','pt','au','hg', &
+   &           'tl','pb','bi','po','at','rn', &
+   & 'fr','ra','ac', &
+   & 'th','pa','u ','np','pu','am','cm','bk','cf','es','fm','md','no', &
+   & 'lr','rf','db','sg','bh','hs','mt','ds','rg','cn', &
+   &           'nh','fl','mc','lv','ts','og' /)
+   esym=elemnt(i)
+end function esym