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 alpha-, beta(1)-, beta(2)-, gamma-, and delta-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 delta-carbon for inside of C36H12. This result is due to the fact that the thermal effect and zero point vibration of delta-carbon and FP stretching motion make adsorbed hydrogen atom go over potential barrier from delta- and beta(1)-carbon for inside of C36H12 more readily. The thermal and nuclear quantum effects are important to evaluate the hydrogen adsorption site on carbon materials. (C) 2011 Elsevier B.V. All rights reserved.