平面波和Wannier函数是固体电子结构的两种常用基组，灵活变换基组和坐标系可以方便理解晶体的电子结构.本文以铁磁半导体单层CrI3为例，通过最大局域化Wannier函数方法把平面波基组变换到局域坐标系下的Wannier基组，并在八面体局域坐标系下清楚地讨论单层CrI3的晶体场劈裂，阐明了体系电子结构和磁性.论文让学生加深了对不同基组概念的理解，并增强了其解决实际问题的能力.

Plane wave and Wannier function are two commonly-used basis sets in electronic structure of solid. The transformation between different basis sets and coordinate systems is helpful for understanding electronic structure. Taking 2D single-layer ferromagnetic semiconductor CrI3 as an illustration example, the present work performs a basis set transformation from plane-wave and Wannier function in localized coordinate system. And then, crystal field splitting of single-layer CrI3 is discussed in localized coordinate system. Moreover, the underlying mechanism of electronic structure and magnetism are also discussed clearly. Our work not only lets student understand the difference between two basis sets, but also increases the ability to solve physical problems.