*deck vh2p
      function vh2p ( r )
c
c >>> vh2p -- potential function in atomic units for the hydrogen
c                molecule-ion (h2 plus)
c
      implicit real*8 (a-h,o-z)
      dimension rh2p(39), ph2p(39), w(39), a(39),b(39),c(39),iop(2)
      common / potpar / vbase, emass, units
c
c     emass = mass of the "electron" in true electron masses
c     units = scale factor to convert to other units if desired
c              units=27.2116 converts to ev
c
c
      data rh2p / .4d0,.6d0,.8d0,1.d0,1.2d0,1.4d0,1.6d0,
     >             1.8d0, 2.0d0,2.2d0,2.4d0,2.6d0,2.8d0,
     >         3.0d0,3.2d0,3.4d0,3.6d0,3.8d0, 4.0d0,4.2d0,
     >         4.4d0,4.6d0,4.8d0, 5.0d0,5.5d0,6.0d0,
     >         6.5d0,7.0d0, 7.5d0,8.0d0,8.5d0,9.0d0,10.d0,
     >         12.d0,14.d0,16.d0,18.d0,20.d0, 30.d0 /
c
      data ph2p / 1.1992150d0, .4951617d0, .1955250d0,
     >            .0482200d0, -.0289717d0,
     >           -.0699793d0, -.0909300d0, -.1002544d0, 
     >           -.1026250d0, -.1008345d0,
     >           -.0965433d0, -.0908346d0, -.0843521d0,
     >           -.0775567d0, -.0707350d0,
     >           -.0640774d0, -.0577072d0, -.0516971d0, 
     >           -.0460800d0, -.0408998d0,
     >           -.0361523d0, -.0318287d0, -.0279267d0, 
     >           -.0244200d0, -.0172318d0,
     >           -.0119633d0, -.0082138d0, -.0055929d0,
     >           -.0037967d0, -.0025700d0,
     >           -.0017429d0, -.0011939d0, -.0005800d0,
     >           -.0001667d0, -.0000714d0,
     >           -.0000350d0, -.0000244d0, -.0000150d0, 0.d0 /
c
      data ncall / 0 /
c
      iflag = 1
      ss = 1.d0
 10   continue
      ncall = ncall + 1
      if ( ncall .gt. 1 ) go to 1
      iop(1) = 5
      iop(2) = 3
      w(39) = 0.d0
      call spl1d1 ( 39, rh2p, ph2p, w, iop, 1, a,b,c  )
 1    continue
c
      vh2p = 0.d0
      rr = r*emass
      if ( rr .gt. 30.d0 ) return
c
      call spl1d2 ( 39, rh2p, ph2p, w, 1, rr, a )
      vh2p = a(iflag)*units*emass*ss
c
      return
c
      entry dvh2p
      iflag = 2
      ss = emass
      go to 10
c
      entry ddvh2p
      iflag = 3
      ss = emass**2
      go to 10
c
      end