Plane-wave Density Functional Theory Study of the Electronic and   Structural Properties of Ionized and Neutral Small Gold Clusters
  We studied the structural and the electronic properties of ionized and neutral small Au clusters via plane wave pseudopotential calculations. All except the anionic heptamer favor one-dimensional zigzag structures or two-dimensional arrangements of triangles. The HOMO-LUMO (highest occupied molecular orbital - lowest unoccupied molecular orbital) gap, the ionization energy, and the electronic affinity exhibit even-odd variation as a function of the cluster size. 
Byeong June Min, Won Chul Shin, Jae Ik Park
cond-mat.mtrl-sci