First-principles quantum analysis of physical and hydrogen storage properties of XTi3H9 (X= Rb, Cs and Fr) hydrides for hydrogen storage and optoelectronic applications

초록

In this study, structural, electronic, optical, mechanical, and gravimetric hydrogen storage capacities (GHSCs) characteristics of XTi3H9 (X = Rb, Cs and Fr) hydrides are calculated using density functional theory (DFT) for their prospective applications in renewable energy. The RbTi3H9, CsTi3H9, and FrTi3H9 exhibit negative formation enthalpies (Delta H) i.e.,-2.39,-2.09, and-1.89 eV/atom, respectively. Metallic nature of XTi3H9 (X = Rb, Cs and Fr) hydrides is evident from merged valence and conduction bands. Efficient absorption of incident light quanta in infrared and visible regions is evident from the calculated optical characteristics of XTi3H9 (X = Rb, Cs and Fr). The calculated elastic constants for XTi3H9 (X = Rb, Cs and Fr) fulfils the Born stability criteria that make them mechanically stable compounds. Ductile nature of XTi3H9 (X = Rb, Cs and Fr) hydrides is evident from their calculated Pugh's ratio that comes out to be more than 1.75. The calculated values of Poisson's ratio (v) show that ionic bonding is dominant in XTi3H9 (X = Rb, Cs and Fr). The calculated values of GHSCs for RbTi3H9, CsTi3H9, and FrTi3H9 are 3.81, 3.18, and 2.41 wt%, respectively. Valuable insights regarding potential applications of XTi3H9 (X = Rb, Cs and Fr) are provided by calculated results to address growing energy demands by manufacturing hydrogen fuel cells.

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