Zhang Guo-Xu, Xie Ying, Yu Hai-Tao, Fu Hong-Gang
Laboratory of Physical Chemistry, School of Chemistry and Materials Science, Heilongjiang University, Harbin 150080, People's Republic of China.
J Comput Chem. 2009 Sep;30(12):1785-98. doi: 10.1002/jcc.21180.
The structural and electronic properties of five terminations of cubic lead titanate (PbTiO3) (110) polar surface were investigated by first-principles total-energy calculations using a periodic slab model. On the PbTiO termination, an anomalous filling of conduction band was observed, whereas on the O2 termination, two surface oxygen atoms formed a peroxo group, demonstrating that the electronic structures of the two stoichiometric terminations undergo significant changes with respect to bulk materials. However, for the three nonstoichiometric TiO-, Pb-, and O-terminated surfaces, their electronic structures are very similar to bulk. Charge redistribution results for the five terminations confirmed that electronic structure and surface composition changes are responsible for their polarity compensation. However, which mechanism actually dominates the stabilization process depends upon energetic considerations. A thermodynamic stability diagram suggested that the two stoichiometric terminations are unstable; however, the three nonstoichiometric terminations can be stabilized in some given regions. Furthermore, this study indicates that the very different stabilities and surface states filling behaviors of the PbTiO3 (110) polar surface with respect to SrTiO3 and BaTiO3 ones seem to originate from the partially covalent characteristics of Pb-O pairs.
采用周期性平板模型，通过第一性原理总能计算研究了立方钛酸铅（PbTiO₃）（110）极性表面的五种终止结构的结构和电子性质。在PbTiO终止结构上，观察到导带的异常填充，而在O₂终止结构上，两个表面氧原子形成了过氧基团，这表明这两种化学计量终止结构的电子结构相对于块状材料发生了显著变化。然而，对于三种非化学计量的TiO-、Pb-和O终止表面，它们的电子结构与块状材料非常相似。五种终止结构的电荷重新分布结果证实，电子结构和表面组成变化是其极性补偿的原因。然而，实际上哪种机制主导稳定过程取决于能量考量。一个热力学稳定性图表明，这两种化学计量终止结构是不稳定的；然而，三种非化学计量终止结构在某些给定区域可以是稳定的。此外，该研究表明，PbTiO₃（110）极性表面相对于SrTiO₃和BaTiO₃表面非常不同的稳定性和表面态填充行为似乎源于Pb - O对的部分共价特性。
