Quantum molecular dynamics simulation of hydrogen diffusion in zirconium hydride

The behavior of hydrogen in zirconium hydride in the high-temperature range has been investigated using the quantum molecular dynamics method. The $\delta$ phases of compositions ZrH$_{1.75}$ and ZrH$_2$ and the liquid phase are considered. The self-diffusion coefficients of hydrogen are calculated as a function of the temperature in the range from 1000 to 6000 K. For the ZrH$_{1.75}$ and ZrH$_2$ hydrides, the obtained values are close to each other. At temperatures of 1000–2000 K, the hydrogen diffusion is determined not only by the mobility of hydrogen atoms but also by the transition from the energetically favorable tetrahedral positions into the excited state. The obtained values of the diffusion coefficients in the temperature range of 1000–1200 K are in good agreement with the experimental data.