Adsorptions of beryllium cluster toward water molecule

An all-electron calculations on Be n H 2 O ( n = 2–13) clusters have been performed by using density functional theory with the generalized gradient approximation at the PW91 level. The results show that H 2 O molecule tend to be adsorbed on the surface of pure Be n clusters in parallel and occupy the outer positions of beryllium clusters. After adsorption, the structure of most clusters changes obviously, and the symmetry is also decreased. The adsorption of beryllium clusters toward H 2 O molecule is relatively strong for n = 6, 7, and relatively weak for n = 4, 10, 13. And, the length of most Be–Be bonds become shorter, while the length of H–O bonds become longer or even break. In other words, the adsorption of water molecule will enhance the Be–Be interaction and weaken the H–O interaction. Compared with pure Be n clusters, the energy gap of Be n H 2 O is significantly improved. With the increase in atom number, the vertical ionization potential of the clusters gradually decreases, while the vertical electron affinities gradually increases. The stability of pure Be n clusters is greatly affected by the adsorption of H 2 O. The H–O bond length, Be–Be bond length and HOMO–LUMO gap of the clusters are changed enormously. In order to consider the effect of weak interaction in water molecule on Be n H 2 O clusters, we use DFT-D to modify the above results. The results of DFT-D are almost the same as that of DFT, and the magic number structure Be 7 H 2 O still exists after adsorption.