DihedralRyckaertBellemans

class DihedralRyckaertBellemans : public feasst::BondFourBody

See the following manuscripts: https://doi.org/10.1039/DC9786600095

As described in the L-OPLS implementation: https://doi.org/10.1021/ct200908r

\(U(\phi)=c_0+c_1(\cos\phi)+c_2(\cos\phi)^2+c_3(\cos\phi)^3\)