The interplay of electronic and nuclear degrees of freedom presents an outstanding problem in condensed matter physics and chemistry. Computational challenges arise especially for large systems, long time scales, in nonequilibrium, or in systems with strong correlations. In this work, we show how downfolding approaches facilitate complexity reduction on the electronic side and thereby boost the simulation of electronic properties and nuclear motion - in particular molecular dynamics (MD) simulations. Three different downfolding strategies based on constraining, unscreening, and combinations thereof are benchmarked against full density functional calculations for selected charge density wave (CDW) systems, namely 1H-TaS$_2$, 1T-TiSe$_2$, 1H-NbS$_2$, and a one-dimensional carbon chain. We find that the downfolded models can reproduce potential energy surfaces on supercells accurately and facilitate computational speedup in MD simulations by about five orders of magnitude in comparison to purely ab initio calculations. For monolayer 1H-TaS$_2$ we report classical replica exchange and quantum path integral MD simulations, revealing the impact of thermal and quantum fluctuations on the CDW transition.
Optical Absorption Study by Ab initio Downfolding Approach: Application to GaAs
我们检查是否本质和定量方面的电子激发光谱被正确捕获的一个有效的低能量模型从{ \em从头算}向下折叠计划。首先采用广义梯度近似下的密度泛函计算方法{ \em ab initio}计算了整体电子结构。利用约束密度泛函理论，在最大定域Wannier函数的基础上，通过下折过程构造了费米能级附近能带的低能有效哈密顿量.利用低能求解器计算了扩展哈伯德模型的低能有效哈密顿量的激发态。作为求解器，我们采用Hartree-Fock近似补充考虑电子-空穴相互作用的单激发组态相互作用方法。目前的三阶段方法适用于GaAs，其中八个频带被保留在有效模型后的下折。所得光谱很好地再现了实验结果，表明我们的下折方案提供了一个令人满意的框架的电子结构计算，特别是对于激发和动力学以及基态。
Theory of ab initio downfolding with arbitrary range electron-phonon coupling
NASA Ames Research Center（美国国家航空航天局艾姆斯研究中心）；University of Oxford（牛津大学）；Tamkang University（淡江大学）；University of Southern California（南加州大学）；University of Colorado Boulder（科罗拉多大学博尔德分校）；Lawrence Berkeley National Laboratory（劳伦斯伯克利国家实验室）；University of California Berkeley（加州大学伯克利分校）；Kavli Energy NanoScience Institute at Berkeley（加州大学伯克利分校卡弗里纳米科学能源研究所）；University of California, Santa Barbara（加州大学圣塔芭芭拉分校）；KBR, Inc.（KBR公司）
Comment on 2501.17230 and 2502.00103 "Phonon-mediated electron attraction in SrTiO3 via the generalized Frohlich and deformation potential mechanisms" and "Theory of ab initio downfolding with arbitrary range electron-phonon coupling"
Derivation of Static Low-Energy Effective Models by ab initio Downfolding Method without Double Counting of Coulomb Correlations: Application to SrVO3, FeSe and FeTe
Ab initio Evidence for Strong Correlation Associated with Mott Proximity in Iron-based Superconductors
我们预测，发现的铁基超导体附近的d6配置（5 Fe 3d轨道填充6个电子）位于一个意想不到的大圆顶的相关电子物质在d5（即，半填充）的莫特绝缘体为中心的脚。这是基于多变量变分蒙特卡罗从头算低能量模型的结果推导的向下折叠。D5莫特接近延伸到随后出现的非相干金属，轨道微分由于莫特物理和洪德规则耦合，其次是反铁磁量子临界，根据现有的实验定量。
Ab initio Derivation of Low-Energy Model for Alkali-Cluster-Loaded Sodalites
利用{ \em ab initio}向下折叠的方法，导出了一个描述碱金属团簇负载的方钠石磁性的有效低能模型。首先，我们构造了一个扩展的哈伯德模型的最大局部化Wannier函数。用约束无规相近似计算了{ \em Ab initio}屏蔽库仑相互作用和交换相互作用。我们发现该系统处于强耦合区，因此海森伯模型是扩展的哈伯德模型的低能模型。我们得到反铁磁耦合$\sim$ $O$（10 K），与实验的自旋磁化率的温度依赖性是一致的。讨论了在推导推广的哈伯德模型时考虑屏蔽效应的重要性。
Dynamical screening effects in correlated materials: plasmon satellites and spectral weight transfers from a Green's function ansatz to extended dynamical mean field theory
