Development and Testing of the OPLS-AA/M Force Field for RNA.Significant improvements have been made to the OPLS-AA force field for modeling RNA.  Simulations of larger systems with noncanonical motifs showed significant structural improvements over the previous OPLS-AA parameters.  The new force field, OPLS-AA/M, is expected to perform competitively with other recent RNA force fields and to be compatible with OPLS-AA models for proteins and small molecules.
OPLS-AA
Development and Testing of the OPLS-AA/M Force Field for RNA.Significant improvements have been made to the OPLS-AA force field for modeling RNA.  The new force field, OPLS-AA/M, is expected to perform competitively with other recent RNA force fields and to be compatible with OPLS-AA models for proteins and small molecules.
OPLS-AA/M
New torsional potentials were optimized based on density functional theory (DFT) scans at the ωB97X-D/6-311++G(d,p) level for potential energy surfaces of the backbone α and γ dihedral angles. 
DFT
New torsional potentials were optimized based on density functional theory (DFT) scans at the ωB97X-D/6-311++G(d,p) level for potential energy surfaces of the backbone α and γ dihedral angles. 
ωB97X-D/6-311++G(d,p)
Results for dinucleotides and tetranucleotides revealed both accurate reproduction of 3 J couplings from NMR and the avoidance of several unphysical states observed with other force fields. 
NMR