The geometric structures, band structures, density of states and optical absorption spectra are studied for cubic and orthorhombic KNbO₃ (C- and O-KNO) crystals by using first-principles calculations. Based on the above calculation results, the mechanisms of photocatalytic properties for both crystals are further theoretically investigated to deepen the understandings of their photocatalytic activity from the electronic level. Calculations for the effective masses of electron and hole are carried out to make comparison in photocatalytic performance between cubic and orthorhombic phases. Optical absorption in cubic phase is found to be stronger than that in orthorhombic phase. C-KNO has smaller electron effective mass, higher mobility of photogenerated electrons, lower electron-hole recombination rate and better light absorption capacity than O-KNO. So, the photocatalytic activity of cubic phase can be higher than orthorhombic one. The present work may be beneficial to explore the series of perovskite photocatalysts.

研究了立方和正交KNbO ₃的几何结构，能带结构，态密度和光吸收光谱通过第一性原理计算获得（C-和O-KNO）晶体。基于以上计算结果，从理论上进一步研究了两种晶体的光催化性能机理，以加深对电子晶体的光催化活性的理解。计算电子和空穴的有效质量，以比较立方相和正交相之间的光催化性能。发现立方相中的光吸收强于正交相中的光吸收。C-KNO具有比O-KNO更低的电子有效质量，更高的光生电子迁移率，更低的电子-空穴复合速率和更好的光吸收能力。因此，立方相的光催化活性可以高于正交晶相。