Bonding properties of calcium gallium arsenide, Ca14GaAs11: a compound containing discrete GaAs4 tetrahedra and a hypervalent As3 polyatomic unit

The authors have theoretically studied the bonding properties of Ca{sub 14}GaAs{sub 11} using the ab initio, self-consistent pseudopotential method within the local density approximation of density functional theory. Ca{sub 14}GaAs{sub 11} is an example of a new series of recently prepared compounds which have the stoichiometry A{sub 14}MPn{sub 11} (A = Ca, Sr, Ba; M = Al, Ga, Mn; Pn = As, Sb, Bi). They have found that the electronic structure and bonding of the Ca{sub 14}GaAs{sub 11} compound are consistent with the Zintl concept. In addition, the GaAs{sub 4} tetrahedra and the linear As{sub 3} groups contained in this compound are isolated units which are not arranged into an extended bonding network. The bonding within the GaAs{sub 4} group is slightly more ionic than the bonding in a GaAs crystal. The linear As{sub 3} unit can be accurately described as a hypervalent three-center, four-electron bonded structure. The A{sub 14}MPn{sub 11} structure type contains the first example of a discrete, hypervalent group 15 linear anion.