Berry: A code for the differentiation of Bloch wavefunctions from DFT calculations

Density functional calculation of electronic structures of materials is one of the most used techniques in theoretical solid state physics. These calculations retrieve single electron wavefunctions and their eigenenergies. The berry suite of programs amplifies the usefulness of DFT by ordering the eigenstates in analytic bands, allowing the differentiation of the wavefunctions in reciprocal space. It can then calculate Berry connections and curvatures and the second harmonic generation conductivity. The berry software is implemented for two dimensional materials and was tested in hBN and InSe. In the near future, more properties and functionalities are expected to be added.材料电子结构的密度泛函计算（Density Functional Calculation）是理论固体物理学领域应用最为广泛的技术手段之一。此类计算可提取单电子波函数及其本征能级。 该Berry程序套件（Berry Suite of Programs）通过将本征态按解析能带进行排序，实现倒易空间中波函数的微分运算，从而拓展了密度泛函理论（Density Functional Theory, DFT）的实用价值。随后，该套件可计算Berry联络、Berry曲率以及二阶谐波产生电导。 这款Berry软件专为二维材料开发，并已在六方氮化硼（hBN）与硒化铟（InSe）体系中完成测试验证。未来，该软件还将新增更多物性与功能模块。