& (-13856*invtk + 324.57 - 47.986*dlogtk)*sqrtis +
akf(i,j,bi,bj)=exp(1590.2*invtk - 12.641 + 1.525*sqrtis +
_RL sqrtis
sqrtis=sqrt(is)
& (-458.79 _d 0*invtk + 3.5913 _d 0) * sqrtis +
& (-13856. _d 0*invtk + 324.57 _d 0 - 47.986 _d 0*dlogtk)*sqrtis+
& 1.525 _d 0*sqrtis + log(1.0 _d 0 - 0.001005 _d 0*s) +
& (-458.79*invtk + 3.5913) * sqrtis +