Toward the development of the potential with angular distortion for halogen bond: a comparison of potential energy surfaces between halogen bond and hydrogen bond.

As noncovalent intermolecular interactions, hydrogen bond (HB) and halogen bond (XB) are attracting increasing attention. In this work, the potential energy surfaces (PESs) of hydrogen and halogen bonds are compared. Twelve halogen-bonded and three hydrogen-bonded models are scanned for analysis using the MP2 level of theory. This work indicates that potential energy surfaces of both HB and XB have angular distortion. The potential well of XB is narrower than that of HB. With the elongation of the bond length, the potential energy surfaces get flatter. The best fitting functions for angular distortion and the flattening character of angular terms are also combined into a modified Buckingham potential. The testing results show that the essential features of the PES, including angular distortion and flattening character, have been reproduced. These results provide a better understanding of halogen and hydrogen bonds and the optimization of halogen bond force fields.