Path integral molecular dynamics for hydrogen adsorption site of zeolite-templated carbon with semi-empirical PM3 potential

To evaluate the adsorption sites of hydrogen atom on buckybowl-like molecule (C36H12), which is a model fragment structure of zeolite-templated carbon (ZTC), we have performed path integral molecular dynamics (PIMD) simulation including thermal and nuclear quantum fluctuations under the semi-empirical PM3 potential. Here we have picked up ten carbons as the adsorption sites of additional hydrogen atom (H*), which are labeled as α-, β1-, β2-, γ-, and δ-carbon from edge to bottom carbon for inside and outside of C36H12, respectively. In the static PM3 calculation and conventional MD simulation the ten stable adsorption sites of H* are obtained both inside and outside of C36H12. In PIMD simulation, on the other hand, the nine stable adsorption sites are obtained, except for δ-carbon for inside of C36H12. This result is due to the fact that the thermal effect and zero point vibration of δ-carbon and H* stretching motion make adsorbed hydrogen atom go over potential barrier from δ- and β1-carbon for inside of C36H12 more readily. The thermal and nuclear quantum effects are important to evaluate the hydrogen adsorption site on carbon materials.