Electronic and Structural Properties of Li₃AlP₂ and Li₃AlAs₂ from First Principles

Mehrdad Dadsetani, Shirin Namjoo

.

DOI: 10.4236/jmp.2011.29110                

Abstract

A detailed analysis of the electronic and structural properties of the filled tetrahedral semiconductors Li₃AlP₂ and Li₃AlAs₂ has been performed, using the full potential linearized augmented plane wave method within the density functional theory. Experimental results about the structural properties, involves the positions of the elements Al and P(As). Since there were not any other efforts about the positions of the Li elements in these compounds, so to our knowledge there was no theoretical study about them till now. In the first step the interactional forces between atoms were minimized. The calculated internal coordinations of atoms agree well with the experimental results. Using these positions we obtained the equilibrium lattice constants, bulk modulus and their pressure derivative. In the second step the electronic properties of Li₃AlP₂ and Li₃AlAs₂ have been studied. The study of total and partial electronic DOS indicate the main contribution of DOS consists of P(As) 3p(4p) and P(As) 3s(4s) states. Our band structure calculation verifies that Li₃AlP₂ is an indirect gap semiconductor with a value of about 2.36 eV between valance band maximum occuring at H point and conduction band minimum occuring at Г point; though the difference between the direct (2.38 eV) and indirect (2.36 eV) is very small. We also found that Li₃AlAs₂ is a direct band gap (1.49 eV) in the center of BZ.

Keywords

Filled Tetrahedral Semiconductors, Electronic Properties, FP-LAPW, DFT

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	R. Juza and F. Hund, “Die Ternaren Nitride Li3AlN2 und Li3GaN2,” Zeitschrift für Anorganische und Allgemeine Chemie, Vol. 257, 1948, pp. 13-25.
[2]	R. Juza, K. Langer and K. V. Benda, “Ternary Nitrides, Phosphides and Arsenides of Lithium,” Angewandte Chemie International Edition, Vol. 7, No. 5, 1968, pp. 360-370. doi:10.1002/anie.196803601
[3]	R. Juza and W. Schulz, “Herstellung und Eigenschaften der Verbindungen Li3AlP2 und Li3AlAs2,” Zeitschrift für Anorganische und Allgemeine Chemie, Vol. 269, 1952, pp. 1-12.
[4]	K. Kuriyama, J. Anzawa and K. Kushida, “Growth and Band Gap of the Filled Tetrahedral Semiconductor of Li3AlP2,” Crystal Growth, Vol. 310, 2008, pp. 2298- 2300.
[5]	M. Dadsetani, S. Namjoo and H. Nejati, “Optical Study of Filled Tetrahedral Compounds Li3AlN2 and Li3GaN2,” Electronic Materials, Vol. 39, No. 8, 2010, pp. 1186- 1193.
[6]	P. Blaha, K. Schwarz, G. K. H. Madsen, D. Kavanicka and J. Luitz, “Wien2k: An Augmented Plane Wave Plus Local Orbitals Program for Calculating Crystal Proper-ties,” Vienna University of Technology, Vienna, 2001.
[7]	P. Perdew, K. Burke and M. Ernzerhof, “Generalized Gradient Approximation Made Simple,” Physical Review Letters, Vol. 77, 1996, pp. 3865-3868. doi:10.1103/PhysRevLett.77.3865
[8]	O. Jepsen and O. K. Andersen, “Improved Tetrahedron Method for Brillouin-Zone Integrations,” Physical Review B, Vol. 49, 1994, pp. 16223-16233.
[9]	F. Birch, “Finite Elastic Strain of Cubic Crystals,” Physical Review B, Vol. 71, 1947, pp. 809-824. doi:10.1103/PhysRev.71.809