The elastic properties and strain effects on crystal structures and bandgap of MZnOS (M = Ca, Sr): A first-principles study

Mechanoluminescence (ML) materials, such as CaZnOS and SrZnOS, show great potential in lighting, sensors, and wearable devices. Despite advances in the understanding of these materials, a detailed first-principles study of the strain-stress relationship and the effects on crystal structure and bandgap is lacking. In this work, we use first-principles calculations to investigate the elastic properties, crystal structure deformations, and bandgap responses under strain for both MZnOS (M = Ca, Sr) compounds, filling the gap in the current understanding of these materials. The elastic constants, elastic modulus and Poisson's ratios for SrZnOS and CaZnOS are calculated, revealing the influence of hydrostatic pressure on lattice parameters and atomic distances. Notably, the stress-strain relationships of SrZnOS and CaZnOS reveal distinct mechanical behaviors under tensile and compressive strains along the [100] and [001] directions. Under compressive stress, especially along the [100] direction, CaZnOS shows greater compressive resistance than SrZnOS. Additionally, strain-induced bandgap variations are observed: SrZnOS exhibits a decrease in bandgap with increasing strain, while CaZnOS shows an initial bandgap widening under compressive loading (0–2.34 GPa) along the [001] direction. Our findings provide new insights into the mechanical and electronic behavior of MZnOS materials, which are crucial for their application in mechanoluminescence and other related fields.