Exploration of hydrides XSrH3(X = Cs, , Fr) for hydrogen storage applications: A first principles study

The strontium based hydrides XSrH3(X 3 (X = Cs ,Fr) , Fr) are investigated in current study using first principles calculations for hydrogen storage applications. The obtained lattice constants for CsSrH3 3 and FrSrH3 3 are 4.88 & Aring; and 4.74 & Aring; respectively. The gravimetric hydrogen storage capacity (Cwt%) C wt % ) for CsSrH3 3 and FrSrH3 3 is 1.33% and 0.95%. The optimized lattice constants are utilized to compute elastic constants and mechanical parameters. The Young's modulus, bulk modulus and shear modulus for FrSrH3 3 is larger than that of CsSrH3 3 revealing the greater mechanical strength of FrSrH3. 3 . The investigations of band structures and density of states indicating the semiconducting nature of with gaps 2.95 eV, 2.52 eV with PBE-GGA and 5.40 eV, 4.54 eV with TB-mBJ for CsSrH3 3 and FrSrH3 3 respectively. The dynamical stability for both hydrides is confirmed from phonon properties. The thermodynamic parameters are calculated under the variation of temperature and pressure. The heat capacities, volume, entropy and thermal expansion coefficient increase with temperature and decrease with pressure.