High-Pressure Investigation on Calcium Borohydride
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 Lab. (BNL), Upton, NY (United States). National Synchrotron Light Source
- Sponsoring Organization:
- Doe - Office Of Science
- DOE Contract Number:
- DE-AC02-98CH10886
- OSTI ID:
- 980237
- Report Number(s):
- BNL-93155-2010-JA; TRN: US1005445
- Journal Information:
- Journal of Physical Chemistry C, Vol. 113, Issue 33; ISSN 1932-7447
- Country of Publication:
- United States
- Language:
- English
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