WanTiBEXOS: A Wannier based Tight Binding code for electronic band structure, excitonic and optoelectronic properties of solids

The Bethe–Salpeter equation (BSE) approach becomes a methodology commonly used for simulating excitonic and optical properties in computer materials sciences. However, BSE approach based directly on first principles demands a high computational cost, being prohibitive for larger systems. In order to overcome this challenge, we have developed WanTiBEXOS, a parallel computational FORTRAN code, constituted of a maximally localized Wannier functions based tight-binding (MLWF-TB) model in conjunction with BSE framework. The MLWF-TB Hamiltonian used in WanTiBEXOS package can be obtained via any density functional theory package interfaced with Wannier90 code. It's expected, due MLWF-TB formalism, a computational time reduction around one or more orders of magnitude in comparison with BSE ab initio implementations. In order to demonstrate its reliability, flexibility, efficiency and versatility of WanTiBEXOS, we simulate electronic and optical property calculations for the representative materials, including conventional bulk semiconductors, perovskites, nano-monolayer materials and van der Waals heterostructures.贝蒂-萨尔佩特方程（Bethe–Salpeter equation, BSE）方法现已成为计算材料科学领域中用于模拟激子与光学特性的主流方法之一。然而，直接基于第一性原理的BSE方法计算成本极高，对于大规模体系而言难以实际应用。为解决这一难题，我们开发了并行计算Fortran代码WanTiBEXOS，该代码将基于最大局域化瓦尼尔函数（maximally localized Wannier functions, MLWF）的紧束缚（tight-binding, TB）模型与BSE框架相结合。WanTiBEXOS工具包中使用的MLWF-TB哈密顿量，可通过任意与Wannier90代码对接的密度泛函理论（density functional theory, DFT）工具包获取。得益于MLWF-TB形式体系，相较于从头算BSE实现方案，该代码可将计算时间缩短1个甚至多个数量级。为验证WanTiBEXOS的可靠性、灵活性、高效性与通用性，我们针对典型材料体系开展了电子与光学特性计算模拟，所涉材料包括传统块体半导体、钙钛矿、纳米单层材料以及范德华异质结。