Structural Phase Transitions of Mg(BH4)2 under Pressure

• Published in: Journal of physical chemistry. C Vol. 113; no. 1; pp. 486 - 492
• Main Authors: George, Lyci, Drozd, Vadym, Saxena, Surendra K, Bardaji, Elisa Gil, Fichtner, Maximilian
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 08.01.2009
• Subjects: 08 HYDROGEN; BEHAVIOR; C: Energy Conversion and Storage; DIAMONDS; HYDROGEN STORAGE; national synchrotron light source; PARTICLE ACCELERATORS; PRESSURE RANGE MEGA PA 10-100; RAMAN SPECTROSCOPY; SPACE; STABILITY; SYNCHROTRONS; TEMPERATURE RANGE 0400-1000 K; WELLS; X-RAY DIFFRACTION
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/jp807842t

The structural stability of Mg(BH4)2, a promising hydrogen storage material, under pressure has been investigated in a diamond anvil cell up to 22 GPa with combined synchrotron X-ray diffraction and Raman spectroscopy. The analyses show a structural phase transition around 2.5 GPa and again around 14.4 GPa. An ambient-pressure phase of Mg(BH4)2 has a hexagonal structure (space group P61, a = 10.047(3) Å, c = 36.34(1) Å, and V = 3176(1) Å3 at 0.2 GPa), which agrees well with early reports. The structure of high-pressure phase is found to be different from reported theoretical predictions; it also does not match the high-temperature phase. The high-pressure polymorph of Mg(BH4)2 is found to be stable on decompression, similar to the case of the high-temperature phase. Raman spectroscopic study shows a similarity in high-pressure behavior of as-prepared Mg(BH4)2 and its high-temperature phase.