TY - JOUR TI - Electronic structure of Ti, Zr, Hf and Sn containing garnets - Materials for immobilization of actinides AU - Rak, Zsolt AU - Ewing, Rodney C. AU - Becker, Udo T2 - Geochimica Et Cosmochimica Acta DA - 2010/// PY - 2010/// VL - 74 IS - 12 SP - A845 ER - TY - JOUR TI - Doping dependence of electronic and mechanical properties of GaSe1-xTex and Ga1-xInxSe from first principles AU - Rak, Zs. AU - Mahanti, S. D. AU - Mandal, Krishna C. AU - Fernelius, N. C. T2 - Physical Review B AB - The electronic and mechanical properties of the hexagonal, layered GaSe doped with Te and In have been studied using first-principles pseudopotential method within density-functional theory. The calculated elastic constants of the end compounds GaSe and InSe compare well with the available experimental and theoretical values. As we go from GaSe to InSe, the elastic constants ${\text{C}}_{13}$, ${\text{C}}_{33}$, and ${\text{C}}_{44}$ increase while ${\text{C}}_{11}$ and ${\text{C}}_{12}$ decrease, suggesting that the crystal becomes stiffer in the direction perpendicular to the atomic layers and the softer in the direction parallel to the layers, as more substitutional In is incorporated in GaSe. The electronic structure and the formation energies of several defects and simple defect complexes are discussed and the calculated charge transition levels are compared to available experimental data. We demonstrate that In doping may play an important role in the observed enhancement in the structural properties of GaSe. Depending on the Fermi energy, In can either substitute for Ga $({\text{In}}_{\text{Ga}})$ or occupy an interstitial position as a triply charged defect $({\text{In}}_{i}^{3+})$. While the substitutional In does not change significantly the electronic and mechanical properties of the host, we find that the shear stiffness of GaSe is considerably increased when In is incorporated as charged interstitial impurity. DA - 2010/// PY - 2010/// DO - 10.1103/PhysRevB.82.155203 VL - 82 IS - 15 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-78149246709&partnerID=MN8TOARS ER - TY - JOUR TI - Defect-induced rigidity enhancement in layered semiconductors AU - Rak, Zs. AU - Mahanti, S. D. AU - Mandal, Krishna C. AU - Fernelius, N. C. T2 - Solid State Communications AB - We discuss the mechanism responsible for the observed improvement in the structural properties of In doped GaSe, a layered material of great current interest. Formation energy calculations show that by tuning the Fermi energy, In can substitute for Ga or can go as an interstitial charged defect$(\text{In}_{\text{i}}^{\text{3+}})$. We find that $\text{In}_{\text{i}}^{\text{3+}}$ dramatically increases the shear stiffness of GaSe, explaining the observed enhancement in the rigidity of In doped p-GaSe. The mechanism responsible for rigidity enhancement discussed here is quite general and applicable to a large class of layered solids with weak interlayer bonding. DA - 2010/// PY - 2010/// DO - 10.1016/j.ssc.2010.04.011 VL - 150 IS - 27-28 SP - 1200-1203 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77954218210&partnerID=MN8TOARS KW - Defects in semiconductors KW - Ab initio KW - Electronic structure KW - Mechanical properties ER -