Structural, energetic and thermodynamic analyses of Ca(BH{sub 4}){sub 2}{center_dot}2NH{sub 3} from first principles calculations

Journal Article · Sun Jan 15 04:00:00 EST 2012 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2011.11.009· OSTI ID:21612873

Pengfei, Yuan; Fei, Wang; Qiang, Sun ^[1]

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1. Center for Clean Energy and Quantum Structures, and School of Physics and Engineering, Zhengzhou University, Zhengzhou, Henan 450052 (China)

Ca(BH{sub 4}){sub 2}{center_dot}2NH{sub 3} is a relatively new compound with potential application in hydrogen storage. Here the fundamental properties of the compound, such as electronic structure, energetic and thermodynamic properties, were comprehensively studied using first-principles calculations. Results from electronic density of states (DOS) and electron localization function (ELF) indicate the covalent bond nature of the N-H bond and the B-H bond. Charge density analyses show weak ionic interactions between the Ca atom and the NH{sub 3} complexes or the (BH{sub 4}){sup -} complexes. The calculated vibration frequencies of B-H and N-H are in good agreement with other theoretical and experimental results. Furthermore, we calculated the reaction enthalpy and reaction Gibbs free energy at a range of temperature 0-700 K. Our results are in good agreement with experimental results in literature. Possible reaction mechanism of the decomposition reaction is proposed. - Graphical Abstract: The crystal structure of this compound and the calculated decomposition reaction free energy for two different reactions: Reac(2):Ca(BH{sub 4}){sub 2} Dot-Operator 2NH{sub 3} Long-Rightwards-Arrow {sup 162 Degree-Sign C}Ca(BH{sub 4}){sub 2} Dot-Operator NH{sub 3}+NH{sub 3} Long-Rightwards-Arrow {sup 230 Degree-Sign C}Ca(BH{sub 4}){sub 2}+2NH{sub 3} Reac(3):Ca(BH{sub 4}){sub 2} Dot-Operator 2NH{sub 3} Long-Rightwards-Arrow {sup 190 Degree-Sign C}1/4Ca(BH{sub 4}){sub 2}+1/4Ca{sub 3}(BN{sub 2}){sub 2}+BN+6H{sub 2}. Highlights: Black-Right-Pointing-Pointer Crystal structure of this compound was studied in detail. Black-Right-Pointing-Pointer Electronic properties were calculated for the first time. Black-Right-Pointing-Pointer Phonon density of states and reaction free energy at different temperatures were first calculated. Black-Right-Pointing-Pointer Possible decomposition mechanism was presented.

• OSTI ID: 21612873
• Journal Information: Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Vol. 185; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
AMMONIA
BORON COMPOUNDS
BORON NITRIDES
CHEMICAL REACTIONS
CRYSTAL STRUCTURE
DECOMPOSITION
DENSITY
ELECTRONIC STRUCTURE
ENERGY
ENTHALPY
FREE ENERGY
FREE ENTHALPY
HYDRIDES
HYDROGEN COMPOUNDS
HYDROGEN STORAGE
INORGANIC COMPOUNDS
INTERACTIONS
KINETICS
NITRIDES
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
PHYSICAL PROPERTIES
PNICTIDES
REACTION HEAT
REACTION KINETICS
STORAGE
THERMODYNAMIC PROPERTIES