Abstract:
We present detailed calculations of formation and thermodynamics transition state
energies of Mgi and Sei interstitial defects in MgSe using generalized gradient approximation
(GGA) and local density approximation (LDA) functional in the frame work of density functional
theory (DFT). For both LDA and GGA the formation energies of Mgi and Sei are
relatively low in all the configurations. The most stable Se interstitial was the tetrahedral (T)
configuration having lower formation energy than the decagonal (D) configuration. The Mgi
and Sei defect introduced transition state levels that had either donor or acceptor levels within
the band gap. Sei acts as a donor or an acceptor and creates levels that were either deep or
shallow depending on the configuration. Sei exhibit negative-U properties and show charge
states metastability in the D configuration. Mgi acts as only shallow donor (+2/ + 1) in both
T and D configurations, in addition we pointed out the role of Mgi as electrically activating
donor.
