First-principles investigation of hydrogen interaction with Cu/WC interface

The WC-Cu composite used as a thermal barrier interlayer between tungsten and CuCrZr heat sink can effectively alleviate the thermal strain mismatch. In this work, the interaction of hydrogen (H) and Cu/WC interface are investigated by performing the first-principles density functional theory calculations. Considering the H solubility in the WC bulk, we found that the most energetically favorable site is not the traditional octahedral interstitial site but is the projection site of octahedral interstitial on the W basal plane. The H diffusion barrier for octahedral interstitial sites and the diffusion path refers to the channel for H penetration and migration into the bulk WC is as high as 0.773 eV. According to the interface calculations, it indicated that the C-terminated interface with the atoms in WC followed the stacking sequence of the Cu (1 1 1) plane can yield the strong adhesion for (1 1 1)Cu/(0 0 0 1)WC interface. Furthermore, the higher dissolution energy for H in this Cu/WC interface indicates no interstitial segregation or trapping site for H in the region due to the localization of interface electrons. Note that the H atom in WC also exhibits a high diffusion barrier. Both of these factors combine to determine that the interface can effectively block the penetration behavior of H into the WC, and the WC-Cu composite materials can use as the H permeation barrier. Besides, our ab initio molecular dynamics (AIMD) simulation also confirmed that H positioned at the interface can spontaneously migrate from the interface to the Cu matrix, and the interface can block the H penetration.