5 巻 (2011) 1 号 p. A0038
Nuclear quantum effects, such as zero-point vibration and tunneling, are important aspect in molecular systems containing light atoms like hydrogen, and it is considered to have substantial influence on their chemical behavior and physical properties. In this report, I will describe the basic idea of path integral molecular dynamics simulations which enables one to compute nuclear quantum effects in complex many-body systems. When the method is combined with ab initio electron structure calculations, the whole molecular entity composed of electrons and nuclei is treated quantum mechanically based on first principles within the framework of Born-Oppenheimer approximation. Using this technique, the quantum nature of strong hydrogen bonds in protonated and deprotonated water clusters have been studied, with a focus on the geometrical isotope effect.