Hydrogen Adsorption Mechanism of Non-equal Atomic Ratio TiZrV NEG Films Surface

Boron neutron capture therapy (BNCT) is a radiotherapy that destroys cancer cells using heavy ions produced by the nuclear reaction of neutrons with boron in the tumors. With the development of accelerator technology, BNCT has developed from reactor based neutron capture therapy to accelerator based boron neutron capture therapy (AB-BNCT). Non-evaporable getter (NEG) is widely used in particle accelerators to achieve ultra-high vacuum and low-pressure gradient. TiZrV NEG film not only has a low activation temperature, but also has many metal active adsorption sites due to the fast diffusion rate of gas molecules in V, and also has good hydrogen absorption kinetics property. TiZrV NEG thin films have been studied extensively. It has been found that the activation temperature is related to the TiZrV atomic ratio. TiZrV NEG thin films with atomic ratios of Ti30%, Zr20% and V50% can be fully activated at 180 ℃ for 24 h. In this paper, for the first time, the density functional theory (DFT) was used to simulate the hydrogen adsorption of this atomic ratio, and the adsorption trends of different adsorption sites, including the changes of adsorption energy, density of states and hydrogen bond length, etc. The research results in this paper are helpful to improve the vacuum and neutron yield stability of AB-BNCT.