Jia Minghao, Cheng Xiyue, Whangbo Myung-Hwan, Hong Maochun, Deng Shuiquan
State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences Fuzhou 350002 P. R. China
University of Chinese Academy of Sciences Beijing 100049 P. R. China.
RSC Adv. 2020 Jul 16;10(44):26479-26485. doi: 10.1039/d0ra03136d. eCollection 2020 Jul 9.
The second harmonic generation (SHG) responses of the paraelectric and ferroelectric phases of KHPO (KDP) were calculated by first-principles density functional theory (DFT) calculations, and the individual atom contributions to the SHG responses were analyzed by the atom response theory (ART). We show that the occurrence of static polarization does not enhance the SHG responses of the ferroelectric KDP, and that the Kleinman symmetry is reasonably well obeyed for the paraelectric phase, but not for the ferroelectric phase despite that the latter has a larger bandgap. This is caused most likely by the fact that the ferroelectric phase has lower-symmetry local structures than does the paraelectric phase. The contribution to the SHG response of an individual K ion is comparable to that of an individual O ion. The contributions of the O and K ions arise overwhelmingly from the polarizable parts of the electronic structure, namely, from the valence bands of the O-2p nonbonding states and from the conduction bands of the K-3d states.
通过第一性原理密度泛函理论（DFT）计算，得出了磷酸二氢钾（KDP）顺电相和铁电相的二次谐波产生（SHG）响应，并运用原子响应理论（ART）分析了单个原子对SHG响应的贡献。我们发现，静态极化的出现并未增强铁电KDP的SHG响应，顺电相相当好地遵循了克莱曼对称性，但铁电相却并非如此，尽管后者具有更大的带隙。这很可能是由于铁电相的局部结构对称性低于顺电相。单个K离子对SHG响应的贡献与单个O离子的贡献相当。O和K离子的贡献绝大多数源于电子结构的可极化部分，即O - 2p非键态的价带和K - 3d态的导带。
