High-Pressure Investigation on Calcium Borohydride

Journal Article · Thu Jan 01 04:00:00 EST 2009 · Journal of Physical Chemistry C

DOI:https://doi.org/10.1021/jp904513j· OSTI ID:980237

George, L; Drozd, V; Bardaji, E; Fichtner, M; Saxena, S

Structural properties of calcium borohydride, Ca(BH{sub 4}){sub 2}, containing {alpha} and {beta} polymorphs are investigated under pressure by in situ synchrotron X-ray diffraction up to 13 GPa and by Raman spectroscopy up to 25 GPa. Results show that the {beta} phase transforms to a highly disordered structure above 10.2 GPa, whereas the {alpha} phase is stable in the pressure range studied. Rietveld analysis of the X-ray diffraction pattern collected at ambient conditions shows that the {alpha} phase is an orthorhombic F2dd structure with lattice parameters a = 8.82(7) {angstrom}, b = 13.05 (10) {angstrom}, c = 7.404(5) {angstrom}, and V = 851.8(10) {angstrom}{sup 3} (64.13 cm{sup 3}/mol). The {beta} phase was checked for all the suggested tetragonal structures, and the best match is obtained with space group P4{sub 2}/m; the lattice parameters are a = 6.88(4) {angstrom}, c = 4.32(5) {angstrom}, and V = 204.82(18) {angstrom}{sup 3} (61.68 cm{sup 3}/mol). Pressure volume data obtained for {alpha}-Ca(BH{sub 4}){sub 2} are fitted with the third-order Birch?Murnaghan equation of state that yields a bulk modulus value of K{sub 0} = 22.95(4) GPa with K{prime}{sub 0} = 2.63(0.5).

• Research Organization: Brookhaven National Laboratory (BNL) National Synchrotron Light Source
• Sponsoring Organization: Doe - Office Of Science
• DOE Contract Number: AC02-98CH10886
• OSTI ID: 980237
• Report Number(s): BNL--93155-2010-JA
• Journal Information: Journal of Physical Chemistry C, Journal Name: Journal of Physical Chemistry C Journal Issue: 33 Vol. 113; ISSN 1932-7447
• Country of Publication: United States
• Language: English

Related Subjects

43 PARTICLE ACCELERATORS
BOROHYDRIDES
CALCIUM
LATTICE PARAMETERS
PRESSURE RANGE
RAMAN SPECTROSCOPY
SPACE GROUPS
SYNCHROTRONS
X-RAY DIFFRACTION
national synchrotron light source