First-principles investigation of YXMnH6 (X = Hg, Zn) complex hydrides: structural, electronic, optical, mechanical, and thermodynamic insights for H2 storage efficiency

Abstract

This paper explores the structural, electronic, mechanical, optical, and thermodynamic characteristics of complex hydrides YXMnH 6 (X = Hg, Zn) to be used in hydrogen storage. The investigation is carried out through first principles calculations. Both compounds are dynamically and thermally stable, as indicated by the lack of negative frequencies in phonon dispersion calculations as well as being confirmed by AIMD simulations at room temperature with minimal fluctuations and no structural degradation. Electronic property-based YHgMnH 6 and YZnMnH 6 compounds exhibit semiconducting behavior, with indirect band gaps of 1.445 eV using PBE-GGA (1.826 eV using mBJ-GGA), and 1.555 eV using PBE-GGA (2.548 eV using mBJ-GGA), respectively. Its structural features indicate that YHgMnH 6 is characterized by the largest lattice constant (6.8623 Å) as compared to YZnMnH 6 (6.6506 Å), as mercury has a higher atomic radius than zinc. According to the Born stability criterion, both compounds are verified to be mechanically stable. 1t is also shown that YZnMnH 6 has a high Young’s modulus and is appropriate for uses requiring hardness and resistance to deformation. Common optical property analysis indicates strong optical response of the ultraviolet region on both compounds; thus, they are good candidates in photovoltaic and optoelectronic applications. The hydrogen storage contents are estimated at 1.73 wt% of YHgMnH 6 and 2.81 wt% of YZnMnH 6 . In general, these findings suggest that YXMnH 6 (X = Hg, Zn) complex hydrides are versatile substances and have the potential to be used in hydrogen storage systems and clean technologies. Further research will be in the field of experimental establishment of YXMnH 6 (X = Hg, Zn) in order to verify existing results and further study its energy applications.