钙钛矿结构中的简谐子软模

The harmonon soft modes in a perovskite structure system

利用复合空间型方法 ,在自由边界条件下解出了钙钛矿结构有限尺寸晶体的简谐振动方程 .计算结果给出了收敛的简谐子谱分布 ,并发现了许多简谐子软模 .用这些软模花样说明了钛酸钡晶体冷却时发生具有a畴和c畴结构的铁电相变 .理论表明铁电相变过程涉及屏蔽电荷的激发及其在界面的缓慢扩散 ,以最后得出各个电畴内部的均匀自发极化 .

By using the complex species method, the harmonic vibrational modes of finite crystals having perovskite structure with free boundary condition were obtained. The convergent distribution function of harmonon was given and many harmonon soft modes were found. These soft modes were used to explain the phenomenon that barium titanate crystal has the structure of a domain and c domain in ferroelectric phase transition when temperature is reduced. The theory indicated that the process of ferroelectric phase transition was involved in the excitation of screen charges and their slow diffusion on the interface, till the homogeneous spontaneous polarization appears within each electric domain.