Dynamics of hydrogen and proton trapped in diamond lattice - A direct molecular orbital dynamics approach

In order to represent the thermal motion of a hydrogen atom and a proton tr apped inside a diamond lattice, trajectories of these oscillators around th e trapping site were simulated using a C26H32 cluster model on the basis of the semi-empirical PM3-MO method combined with the direct molecular orbita l (MO) dynamics calculation. Trapping occurs in the tetrahedral (T) interst itial site for both the hydrogen atom and the proton, With increasing tempe rature from 0 to 600 K the hydrogen and proton show an increase in amplitud e of vibration due to the thermal activation. The hydrogen atom vibrates on ly around the trapping site up to 600 K, which leads to a decrease in the s pin density for the atom from 0.971 at 0 K to 0.963 at 600 K, On the other hand, the proton is observed to transfer to the next tetrahedral site, exce eding the potential energy barrier at 600 K. No other trapping sites can be found in this process.