Ab initio calculations on nuclear quadrupole interactions of Ga and N nuclei in GaN of ionic crystal

This paper presents the results of our calculation of nuclear quadrupole coupling constant (NQCC) of 69,71Ga and 14N on wurtzite GaN crystal using the Hartree-Fock Roothaan Molecular Cluster procedure. We employed Ga4N4H18 cluster as well as the (GaN4)9- and the (NGa4)9+ clusters surrounded by 1160 external Ga3+ and N3- ions in 15 A radius lattice to simulate the covalent bonding and ionic bonding among the constituent atoms in the solid-state system and to calculate the electronic structure and the associated nuclear quadrupole interaction properties of 14N and 69,71Ga. The nuclear quadrupole coupling constant (NQCC) e2qQ/h for 69Ga with a value of its Q as 0.168 barns was found to be 2.98 MHz in the (GaN4)9- cluster and 34.43 MHz in the Ga4N4H18 cluster. The e2qQ/h for the 14N in the (NGa4)9+ cluster representing the ionic bonding was found to be 0.0303 MHz using the nuclear quadrupole moment of 14N nucleus as 0.0193 barns. The calculated NQI parameters from the (GaN4)9- and the (NGa4)9+ clusters agree well with the experimental values indicating the existence of the significant ionic bonding between the constituent atoms in the solid-state system.