# Stability and hydrogen storage potential of zirconium-based A2ZrH6 (A = Na, K) hydrides: a DFT and AIMD investigation

## TL;DR

This study explores zirconium-based hydrides for hydrogen storage, finding they are stable and efficient materials for future energy systems.

## Contribution

The paper introduces new insights into the stability and hydrogen storage potential of A2ZrH6 (A = Na, K) perovskite hydrides using DFT and AIMD.

## Key findings

- Na2ZrH6 and K2ZrH6 show hydrogen storage capacities of 4.22 and 3.45 wt% respectively.
- AIMD simulations confirm thermal stability at 300 K for both hydrides.
- Electronic structure calculations reveal band gaps suitable for photovoltaic applications.

## Abstract

Perovskite-based materials offer considerable potential for efficient, stable and environmentally sustainable hydrogen storage technologies. In this work an inclusive density functional theory (DFT) investigation was conducted to evaluate the structural, mechanical, optoelectronic and thermodynamic features of A2ZrH6 (A = Na, K) perovskite hydrides. Structural analysis reveals the stable cubic Fm3̄m symmetry, supported by favorable tolerance factors (0.92–0.99) and negative formation energies endorsing thermodynamic stability. Ab initio molecular dynamics (AIMD) simulations assure thermal stability at 300 K without significant structural distortion. Na2ZrH6 and K2ZrH6 exhibit notable hydrogen storage characteristics, achieving 4.22 and 3.45 wt% capacities with desorption temperatures of 441.39 and 258.91 K respectively. Mechanical analysis confirms elastic and Born stability with Poisson's ratios of 0.14 (Na2ZrH6) and 0.25 (K2ZrH6) and B/G ratios of 1.06 and 1.66 indicating brittle behavior. Electronic structure calculations confirm the band gaps of 1.25 and 1.87 eV while optical investigations indicate the suitability of these hydrides for photovoltaic applications. These results highlight A2ZrH6 (A = Na, K) perovskite hydrides as viable and efficient materials for next-generation hydrogen storage and energy conversion systems.

Perovskite-based materials offer considerable potential for efficient, stable and environmentally sustainable hydrogen storage technologies.