First principles study of chromium-based hydrides for optoelectronics and hydrogen storage applications

Abstract

The first-principles study employed on chromium-based hydride XCrH3 (X: Na, K) is the first time studied and investigated different physical properties incorporated for optoelectronics and hydrogen storage applications. The structural properties results revealed that these materials have cubic phases, with lattice constants are 3.54 Å (NaCrH3), and 3.74 Å (KCrH3), which was also confirmed by the XRD analysis. The XRD results revealed that the intensity of KCrH3 is shifted towards to lower angle (2θ) degree due to high lattice constants and inter-planner distance. Moreover, both materials exhibited thermodynamically and mechanically stable due to negative formation energy, and elastic constants, and obeyed the Born approximation criteria. The phonons dispersion curve shows that XCrH3 is dynamically stable due to no imaginary frequency presence. Electronic properties found that current materials have metallic characteristics, due to zero band-gap energy, which plays a vital role in hydrogen storage applications. Magnetic properties exhibited paramagnetic behavior of current materials highly contributed to hydrogen storage application due to unpaired electrons and studied materials have spin-polarized magnetic nature. However, elastic properties confirmed that these materials are found hard, and brittle, with an ionic bonding nature between the atoms, and an anisotropic character. Besides this, different optical parameters have studied like as conductivity, absorption coefficient, refractive index, reflectance, and loss function and the results revealed that the examined materials dominated the role in LED, sensors, solar cells, and optoelectronics applications. Thermal analysis revealed that increasing temperature increases energy and entropy but decreases free energy. Among the studied materials, NaCrH3 has a high gravimetric ratio of 3.87 wt%, and KCrH3 is 3.21 wt%. These materials provided new potential for hydrogen storage applications.