  Past experiments about hydrogen absorption in niobium have revealed specific
properties about interactions between interstitial hydrogen atoms. It has been
reported that there are long-range attractive and short-range repulsive
interactions between interstitial hydrogen atoms in niobium. It has also been
reported that these interactions are of many-body nature. While previous
understanding of these interactions is based on experimental inferences from
past experiments, through these calculations, for the first time, we can
understand the nature of the interactions at a fundamental level. In this work,
we use Density Functional Theory calculations to study the interactions of
interstitial hydrogen atoms in niobium. We report here that these interactions
are a combination of an attractive, indirect image interaction and a repulsive,
direct interaction. Through our calculations, we also infer here that these
interactions indeed have many-body characteristics.
