Theoretical investigations on the elastic, electronic and thermal properties of orthorhombic Li2CdGeS4 under pressure

• Published in: Journal of alloys and compounds Vol. 581; pp. 867 - 872
• Main Authors: Li, Xiaofeng, Peng, Weimin, Fu, Hongzhi
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 25.12.2013; Elsevier
• Subjects: Alloys; Anisotropy; Applied sciences; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Elastic constants; Elasticity; Elasticity. Plasticity; Electron states; Electronic structure; Electronics; Exact sciences and technology; Li2CdGeS4; Mathematical models; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metals. Metallurgy; Methods of electronic structure calculations; Optical properties; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of bulk materials and thin films; Photons; Physics; Thermal expansion; thermomechanical effects and density; Thermal properties; Thermal properties of condensed matter; Thermal properties of crystalline solids; Thermal properties; Elasticity; Electronic structure; Li2CdGeS4; Elastic constant; Pseudopotential; Grueneisen constant; Specific heat; Energy gap; Optical properties; Li; Optical absorption; Elastic modulus; Band structure; Electronic properties; Heat capacity; CdGeS; Debye approximation; Absorption spectrum; Pressure effect; Anisotropy; High energy; Orthorhombic lattices; APW calculation; Aggregate; Local density approximation
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2013.07.043

•The normalized lattice parameters indicated that compression along b-axis is largest and that along a-axis is smallest.•Li2CdGeS4 is not mechanically stable above about 8.6GPa.•The electronic structure and optical properties of Li2CdGeS4 are investigated under pressure.•The thermodynamic properties of Li2CdGeS4 are also obtained successfully. The structural, elastic, electronic, optical and thermal properties of orthorhombic Li2CdGeS4 have been performed by the first-principles plane-wave pseudopotential method. The calculated structural parameters and elastic constants at zero pressure and temperature are in good agreement with the available theoretical result. The dependence of the elastic constants Cij, the aggregate elastic modulus B, G and the anisotropies of Li2CdGeS4 under pressure have been investigated. By the elastic stability criteria, it is predicted that orthorhombic Li2CdGeS4 is not stable above 8.6GPa. The electronic band structures and optical properties of Li2CdGeS4 under pressure are studied. It is found that a direct band gap at zero pressure induced by the G–G transition is presented, which is 2.421eV (LDA). Moreover, the direct energy band gap (G–G) transforms to the indirect energy gap (along G–X point) at about 4GPa. The refractive and the absorption indexes under pressure suggest that the strong absorption spectrum appears mostly in the ultra-violet region, and the optical absorption decreases with photon energy in the high energy range. Finally, by using a quasi-harmonic Debye model, the heat capacity and Grüneisen parameter are also obtained successfully.