# First-principles study on various point defects formed by hydrogen and helium atoms in tungsten

## TL;DR

This study uses first-principles calculations to explore how hydrogen and helium atoms form different point defects in tungsten, revealing their preferred sites, interactions, and formation energies.

## Contribution

It provides new insights into the defect formation and interactions of hydrogen and helium in tungsten using first-principles methods.

## Key findings

- Hydrogen prefers tetrahedral interstitial sites in tungsten.
- Helium prefers substitutional sites in tungsten.
- Hydrogen atoms tend to stay apart after relaxation, helium atoms stay close.

## Abstract

The different point defects formed by two hydrogen atoms or two helium atoms in tungsten were investigated through first-principles calculation. The energetically favorable site for a hydrogen atom is tetrahedral interstitial site while substitutional site is the most preferred site for a helium atom. The formation energies of two hydrogen or helium atoms are determined by their positions, and there are not a multiple of a single atom's. After relaxation, two adjacent hydrogen atoms are away from each other while helium atoms are close to. The reasons for the interaction between two hydrogen or helium atoms are also discussed.