中文摘要：

利用第一性原理研究了低温及高温相Ca（BH4）2络合物的电子结构、晶格振动及其反应焓．计算结果表明：低温及高温相Ca（BH4）2中Ca^＋2与[BH4]^-以离子键形式相结合，[BH4]^-离子中B原子和H原子以共价键形式相结合，对该共价键有贡献的主要是B原子的2p轨道电子，H原子的1s轨道电子．Ca（BH4）2可能的反应路径为：Ca（BH4）2→2CaH2＋CaB6＋10H2，该反应在300K下反应焓为43．22kJ／molH2．拉伸B-H键所对应的声子频率较高，其值为2360-2500cm^-1，这可能是导致B—H键断裂释放氢气需要较高温度的主要原因之一．

英文摘要：

The electronic structure, lattice dynamic and reaction enthalpies of low-temperature and high-temperature phases of Ca（BH4）2 complex have been studied using first-principle. The calculation results show that, for both low and high-temperature phases of Ca（BH4）2 complex, the interaction between Ca^＋2 and [BH4]^- anion has an ionic character, and the interaction between B and H is covalent. This covalent bond is dominated by B 2p and H 1s orbitals. The possible dehydrogenation process is 3Ca（BH4）2→2CaH2＋CaB6＋10H2, and the reaction enthalpy is 43.22 kJ/mol H2. The lattice dynamic calculations show that the phonon modes of stretching [BH4]^- anion are in 2360-2500 cm^-1 , these high phonon modes indicate that they need high energies to breakup of B-H bond in [BH4]^- anion.