High-pressure polymorphs of Li(2)BeH(4) predicted by first-principles calculations

Area of Science:

• Materials Science
• Solid-State Chemistry
• Computational Chemistry

Background:

• Lithium beryllium hydrides (Li(2)BeH(4)) are hydrogen storage materials.
• Understanding high-pressure phases is crucial for exploring novel material properties and applications.
• Previous studies have proposed potential high-pressure structures for Li(2)BeH(4).

Purpose of the Study:

• To predict and characterize novel high-pressure polymorphs of lithium beryllium hydrides (Li(2)BeH(4)).
• To determine the energetic stability and transition pressures of these predicted phases.
• To refine the understanding of structural transitions under high pressure.

Main Methods:

• First-principles calculations were employed to predict crystal structures.
• Density Functional Theory (DFT) was used for electronic structure and energy calculations.
• Thermodynamic stability and phase transitions were investigated as a function of pressure.

Main Results:

• Two new orthorhombic high-pressure polymorphs of Li(2)BeH(4) were predicted: β-Na(2)SO(4)-type and La(2)NiO(4)-type structures.
• The β-Na(2)SO(4)-type structure becomes more stable than the ambient α-Li(2)BeH(4) phase above 7.2 GPa, correlating well with experimental data (9.1 GPa).
• A further transition to the La(2)NiO(4)-type structure is predicted at 28.8 GPa, with significant volume contractions at both transitions.

Conclusions:

• The study successfully predicted two novel high-pressure polymorphs for Li(2)BeH(4).
• The findings provide crucial insights into the pressure-induced structural evolution of lithium beryllium hydrides.
• The previously proposed Cs(2)MgH(4)-type structure was ruled out as a high-pressure candidate.