Abstract
We present a new force field derived from a modification of the universal force field (UFF). Although the UFF is widely used in the field of molecular mechanics and dynamics, it is unsuitable for such applications as correctly estimating the hydrogen bond. We have derived a new variable-charge force field from the UFF by incorporating a modified charge equilibration (MQEq) method for the electrostatic term and a scale factor for the van der Waals term, which we refer to as the extended universal force field (XUFF). The MQEq parameters and the scale factor are optimized. We have implemented the XUFF in the ABINIT-MP program and show that the XUFF is very useful for analyzing the conformation of a molecular system such as hydrogen-bonding molecular pairs, ligands, and proteins.
