c
      subroutine potbo(rab,rbc,rac,v)
c
      implicit real*8(a-h,o-z)
      common/b21/ de1,de2,de3,re1,re2,re3
     >   ,b1,b2,b3
      common/b22/a11,a12,a13,a21,a22,a23,a31,a32,a33,a14,a24,a34
      common/btanh/ref1,ref2,ref3,sl1,sl2,sl3,r01,r02,r03
      common/repuls/a,n1,n2,n3
      common/refine/agb,cgbx,cgby,cgbz,agw,cgwx,cgwy,cgwz,
     >               xn0b,yn0b,zn0b,xn0w,yn0w,zn0w
c
      x=rab
      y=rbc
      z=rac
c
      if(x.le.0.d0)x=1.d-4
      if(y.le.0.d0)y=1.d-4
      if(z.le.0.d0)z=1.d-4
c
c hyperbolic tangent damping functions
c
c      w1=.5d0*(1d0+tanh(sl1*(x-ref1)))
c      w2=.5d0*(1d0+tanh(sl2*(y-ref2)))
c      w3=.5d0*(1d0+tanh(sl2*(z-ref3)))
c      ww=w1*w2*w3
c
c  diatomic terms and their corrections
c
      v=0.d0
       ex=exp(-b1*(x-re1))
       ey=exp(-b2*(y-re2))
       ez=exp(-b3*(z-re3))
       vxx=-de1*ex*(a11+ex*(a12+ex*(a13+ex*a14)))
       vyy=-de2*ey*(a21+ey*(a22+ey*(a23+ey*a24)))
       vzz=-de3*ez*(a31+ez*(a32+ez*(a33+ez*a34)))
       tx=de1*ex**n1
       ty=de2*ey**n2
       tz=de3*ez**n3
       vxx=vxx+a*tx
       vyy=vyy+a*ty
       vzz=vzz+a*tz
       vbiat=vxx+vyy+vzz
c       write(6,*)n1,n2,n3,tx,ty,tx
c
c  the triatomic term and its corrections
c
        call pol3(x,y,z,v3xyz)
c
c      if(x.lt.re1)x=re1
c      if(y.lt.re2)y=re2
c      if(z.lt.re3)z=re3
c      call pol3(x,y,z,v3re)
c
c      vtriat=ww*v3xyz+(1.d0-ww)*v3re
       vcbar=exp(-cgbx*(ex-xn0b)*(ex-xn0b))*
     > exp(-cgby*(ey-yn0b)*(ey-yn0b))*
     > exp(-cgbz*(ez-zn0b)*(ez-zn0b))
       vcwel=exp(-cgwx*(ex-xn0w)*(ex-xn0w))*
     > exp(-cgwy*(ey-yn0w)*(ey-yn0w))*
     > exp(-cgwz*(ez-zn0w)*(ez-zn0w))
       vtriat=.9935d0*v3xyz + agb*vcbar + agw*vcwel
c      if(vcbar.gt..001d0.or.vcwel.gt..001d0)write(6,*)agb,vcbar,agw,vcwel
       v=vbiat+vtriat
       if(v.gt.331.d0)v=331.0d0+log(v-330.0d0)
       vshow=v+de2
c     write(8,11)x,y,z,sx,sy,sz,vxx,vyy,vzz,vtriat,vshow
11      format(6f5.2,5f8.2)
      end