An ab-initio investigation of mechanical and thermodynamic properties of Ag2MgSn(S/Se)4 in kesterite and stannite phases

• Published in: Applied physics. A, Materials science & processing Vol. 127; no. 8
• Main Authors: Srivastava, A., Tripathy, S. K., Lenka, T. R., Menon, P. S., Lin, F., Aberle, A. G.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01-08-2021; Springer Nature B.V
• Subjects: Applied physics; Bonding strength; Characterization and Evaluation of Materials; Condensed Matter Physics; Constants; Crystal structure; Crystallinity; Density functional theory; Dispersion curve analysis; Elastic properties; Machines; Manufacturing; Materials science; Mathematical analysis; Modulus of elasticity; Nanotechnology; Optical and Electronic Materials; Phonons; Photovoltaic cells; Physics; Physics and Astronomy; Processes; Solar cells; Stability analysis; Stability criteria; Structural stability; Surfaces and Interfaces; Thermal expansion; Thermodynamic properties; Thin Films; Elastic constants; DFT; Thermodynamic properties; Phonon calculations
• ISSN: 0947-8396; 1432-0630
• DOI: 10.1007/s00339-021-04741-0

In this work, mechanical and thermodynamic properties and phonon calculations of quaternary chalcogenide material Ag
2
MgSn(S/Se)
4
in kesterite and stannite phases are calculated using density functional theory with generalized gradient approximation (GGA) functional. Elastic constants are calculated for all the four crystal structures, and it is found that they are mechanically stable in accordance with Born–Huang stability criterion. Also, it is observed that the strength of bonds along the [1 0 0] and [0 1 0] crystalline directions is as strong as the bonds in the [0 0 1] crystalline direction for all structures. The sum of elastic constants
C
11
and
C
12
is greater than
C
33
showing that elastic modulus calculated in the (0 0 1) plane is more compared to its values along the c-axis. With Pugh’s theory analysis, it is found that the B/G ratio is greater than 1.75 for all four structures, and they are ductile in nature. Using the Debye model, vibrational heat capacity at constant volume and coefficient of thermal expansion are studied in the temperature range of 0–1200 K for all four structures. Also, the vibrational modes and phonon dispersion curve along the high symmetry point (Z-Γ-X-P-Γ-N) are analysed to investigate the stability of the structures. These findings should be useful in the fabrication of thin-film solar cells using these materials as absorber layer.