Questaal: A package of electronic structure methods based on the linear muffin-tin orbital technique

This paper summarises the theory and functionality behind Questaal, an open-source suite of codes for calculating the electronic structure and related properties of materials from first principles. The formalism of the linearised muffin-tin orbital (LMTO) method is revisited in detail and developed further by the introduction of short-ranged tight-binding basis functions for full-potential calculations. The LMTO method is presented in both Green’s function and wave function formulations for bulk and layered systems. The suite’s full-potential LMTO code uses a sophisticated basis and augmentation method that allows an efficient and precise solution to the band problem at different levels of theory, most importantly density functional theory, LDA +U, quasi-particle self-consistent GW and combinations of these with dynamical mean field theory. This paper details the technical and theoretical bases of these methods, their implementation in Questaal, and provides an overview of the code’s design and capabilities.本文综述了开源代码套件Questaal的理论根基与功能全貌，该套件是一套可从第一性原理出发计算材料电子结构及相关物性的开源代码集合。本文对线性化muffin-tin轨道（linearised muffin-tin orbital, LMTO）方法的形式体系展开了详细回顾，并通过引入适配全势计算的短程紧束缚基函数，对该方法进行了进一步拓展。针对块体与层状体系，本文分别从格林函数（Green’s function）与波函数两种形式对LMTO方法进行了系统阐述。该套件的全势LMTO代码采用了一套精密的基组与增强方案，能够在不同理论层级下高效且精准地求解能带问题，其中核心理论方法包括密度泛函理论、LDA+U、准粒子自洽GW方法，以及上述方法与动力学平均场理论的联合应用。本文详细阐释了上述方法的技术与理论基础、其在Questaal中的实现细节，并对该代码的设计架构与功能特性进行了全面概述。