New potential stable structures of XMgn (X = Ge, C, Sn; n=2-12) clusters: XMg8 with high stability.

Several potential stable structures of X-doped magnesium (X= Ge, C, Sn) clusters have been fully investigated by using CALYPSO structure searching software together with density functional theory (DFT) calculations. XMgn (X= Ge, C, Sn; n = 3-7) clusters have similar geometric structure grows in tetrahedron, while the structures of XMgn (X= Ge, C, Sn; n = 8 - 12) are based on a kind of tower-like geometry. Interestingly, the relative stability computations indicate that XMg8 (X= Ge, C, Sn) are more stable than other clusters, and thus can be identified as magic clusters. In addition, XMg8's (X= Ge, C, Sn) high stability and atomic interactions contained in structures are studied through their electronic localization function (ELF) and molecular orbitals (MOs). It is shown that the covalent σ bond interaction of X-Mg and Mg-Mg are mainly responsible for their robust stability. Finally, the theoretical calculations of IR and Raman spectra of XMg8 (X= Ge, C, Sn) clusters were implemented for guiding further experimental observation.