Structural Phase Stability in Fluorinated Calcium Hydride

TL;DR

This study uses ab-initio calculations to explore how fluorination affects the structural stability, electronic properties, and bonding in calcium hydride, revealing phase transitions and enhanced stability.

Contribution

It provides new insights into fluorination-induced phase stability and electronic structure changes in calcium hydride using density functional theory.

Findings

Phase transition from orthorhombic to cubic at 18% fluorine doping

CaH2-xFx systems are highly stable and insulating

Fluorination facilitates easier removal of nearby hydrogen atoms

Abstract

In order to improve the hydrogen storage properties of calcium hydride (CaH2), we have tuned its thermodynamical properties through fluorination. Using ab-initio total energy calculations based on density functional theory, the structural stability, electronic structure and chemical bonding of CaH2-xFx systems are investigated. The phase transition of fluorinated systems from orthorhombic to cubic structure has been observed at 18% fluorine doped CaH2. The phase stability analysis shows that CaH2-xFx systems are highly stable and the stability is directly correlating with their ionicity. Density of states (DOS) plot reveals that CaH2-xFx systems are insulators. Partial DOS and charge density analyses conclude that these systems are governed by ionic bonding. Our results show that H closer to F can be removed more easily than that far away from F and this is due to disproportionation induced in the bonding interaction by fluorination.