锂氧化物主体和表面相的稳定性研究

Thermodynamic Stabilities of Lithium Oxides in Bulk and Surface Phases

本文通过密度泛函理论以及声子模型,系统地研究了金属锂、氧化锂、过氧化锂、超氧化锂和臭氧化锂在不同温度下的热力学函数值以及它们在不同温度和氧气分压条件下的稳定性,并绘制了锂氧化物的热力学相图.另外,理论研究了氧气存在下各种锂氧化物表面相的稳定性,对于符合化学计量的表面,其表面能从小到大的顺序为(111)<(110)<(211)<(221)<(210)<(100).根据各表面的表面能相对大小,绘制了金属锂氧化物的表面热力学平衡曲线,并由Gibbs-Wulff晶体平衡形态理论,获得了氧化锂和过氧化锂的晶体形貌.

Thermodynamic properties and stabilities of lithium metal,lithia,lithium peroxide, lithium superoxide and lithium ozonide were systematically investigated by a density functional theory and a phonon model at different temperatures and partial oxygen fugacities.The theoretical phase diagram of lithium oxides were obtained.We also investigated the stabilities of various surfaces of lithium oxides under different pressures of oxygen.For the stoichiometric surfaces,the surface energies are in the order:(111)<(110)<(211)<(221)<(210)<(100).The thermodynamic equilibrium curves as well as the morphology of lithia and lithium peroxide crystals were obtained by the Gibbs-Wulff crystal equilibrium theory according to the value of the surface energy of each surface.