A density-functional study of the structure and self-organization in spin clusters

Abstract In a theoretical investigation of the interplay between spin and the geometric arrangement of atoms clustering on a van der Waal solid, we use first-principles methods to investigate the structural, electronic and magnetic properties of small free clusters of cesium. The structural and electronic properties of small Csn (n⩽8) clusters of low-and high-spin multiplicity are studied within the generalized gradient approximation of density-functional theory. We find that although higher spin states are not favored for the cesium dimer and trimer (such states are not bound for Cs2 and Cs3); those of the tetramer and larger clusters show small singlet–triplet energy differences. In particular, we find two-dimensional structural forms among the optimal isomers of Csn clusters for both the low and the higher spin states up to size n=6. The transition to optimal three-dimensional (3-D) structures occurs at Cs7, where the two-dimensional geometry is significantly (0.36 eV) higher in energy than the lowest energy 3-D structure. There is also a distinct preference for the lowest spin states for n⩾7. An analysis of these trends is presented.