... frequency of the Gen+1 and GenAl equilibrium geometry Cluster Ge2 GeAl Ge3 Ge 2Al Ge4 Ge 3Al Ge5 Ge 4Al Ge6 Ge 5Al Ge7 Ge 6Al Ge8 Ge 7Al Ge9 Ge 8Al Ge1 0 Ge 9Al Isomer 1-a0 1-a 2-a0 2-a 2-b 2-c 3-a0 3-a ... E½Gen Al ¼ E½Genþ1 Al þ E½GenÀ1 Al À 2E½Gen Al Ef ðGen Al ¼ EðGenÀ1 Al þ E Ge À EðGen Al ð6Þ ð5Þ where E [Ge] , E [Al] , E[GenÀ 1Al] , E[GenAl], and E[Gen+ 1Al] , respectively, are the total ... the Ge 5Al, Ge 7Al and Ge 9Al clusters have a smaller HOMO–LUMO gap As shown in Fig 5, for GeAl, Ge 4Al and Ge 7Al clusters, the HOMO–LUMO gaps of GenAl clusters are usually larger than those of Gen+1...