On each monolayer, the metal-substrate interaction of Non-equivalent-MH is larger than the binding energy. This arises from the distortion term, E distortion , being larger than the metal-metal interaction energy for this configuration on all monolayers. This distortion is caused by both Cu adatoms being bonded to the same chalcogen, which lies between both Cu adsorption sites. Although this is seen on both the selenide and telluride monolayer, the monolayer is not strained to the same extent. The increased atomic radius of both selenium and tellurium, compared to sulphur means that much less strain is put on the monolayer in order to accommodate this adsorption mode. This is evident from small E distortion of only 0.08 and 0.10 on WSe 2 and WTe 2 , compared to 0.43 eV on WS 2 . Interestingly, although the Cu-chalcogen bonds are longest on the WTe 2 monolayer, the distortion caused by the adsorbed atoms is slightly larger than that on the WSe 2 monolayers, again showing that despite an increased distance between Cu and chalcogen atoms on WTe 2 , the interaction is slightly stronger than that on WSe 2 .