1.  线性响应含时密度泛函理论，GW近似，Bethe-Salpeter方程等激发态计算方法开发 

GW近似是Lars Hedin在1965年提出的一种计算准粒子自能的方法，可用于准确计算弱关联物质的准粒子能带结构。Bethe-Salpeter Equation （BSE）定量描述了物质中光激发电子-空穴对的激子效应，被用于精确计算物质的光吸收谱等性质。近年来GW和BSE方法被广泛应用于计算物质的激发态性质。但是，GW和BSE方法计算量远高于密度泛函理论（DFT)，一般多用于小尺寸的系统（小于50个原子）。我们希望通过改进计算方法，在保证GW/BSE方法的精度同时，提升计算效率，处理更大更复杂的系统。

主要成果：

- 提出了Energy-integration方法，测试发现可以提升GW计算效率一到两个数量级。

- 参与了NanoGW软件的开发（DOE CODE: Project Metadata for Code ID 60032 (osti.gov)）。

相关论文

W Gao, Z Tang, J Zhao, JR Chelikowsky, Efficient Full-frequency GW Calculations using a Lanczos Method

Physical Review Letters (Editor’s Suggestion) (2024), arXiv:2310.20103 (2023) 

W. Gao*, W. Xia, P. Zhang, J. Chelikowsky, J. Zhao, Numerical methods for efficient GW calculations and the applications in low-dimensional systems (Review article)

Electronic Structure 4 (2), 023003 (2022)

W. Gao, W. Xia, X. Gao, P. Zhang, Speeding up GW calculations to meet the challenge of large scale quasiparticle predictions

Scientific Report 6, Article Number: 36849 (2016) 

W. Gao, W. Xia, Y. Wu, W. Ren, X. Gao, P. Zhang, Quasiparticle band structures of CuCl, CuBr, AgCl, and AgBr: The extreme case

Phys. Rev. B 98 (4), 045108 (2018) 

W. Xia, W. Gao, G. Lopez-Candales, Y. Wu, W. Ren, W. Zhang, and P. Zhang, Combined sub-sampling and analytical integration for efficient large-scale GW calculations for 2D systems

npj Computational Materials 6 (1), 1-9 (2020) 

W. Gao and J. Chelikowsky, Accelerating time-dependent density functional theory and GW calculations for molecules and nanoclusters with symmetry adapted interpolative separable density fitting

Journal of chemical theory and computation 16 (4), 2216-2223 (2020) 

2. 物质的第一性原理计算模拟 

应用第一性原理计算方法来研究和预测物质性质（如电子能带，声子谱，光吸收谱，晶体结构稳定性和磁性等）。研究中主要使用的理论工具包括密度泛函理论（DFT），密度泛函微扰理论（DFPT），量子多体理论（GW approximation和Bethe-Salpeter方程）和分子动力学等。主要研究的材料包括二维磁性和铁电材料，过渡金属化合物，光伏材料等。

相关论文

F Zhang, W Gao*, GJ Cruz, Y Sun, P Zhang, J Zhao, Giant excitonic effects in vacancy-ordered double perovskites

Physical Review B 107 (23), 235119 (2023)

Y. Zhao, Q. Liu, F. Zhang, X. Jiang, W. Gao*, J. Zhao, Multiferroicity in a Two-Dimensional Non-van der Waals Crystal of AgCr₂X₄ (X = S or Se)

The Journal of Physical Chemistry Letters 13 (48), 11346-11353 (2022)

W. Gao, F. H. Jornada, M. Del Ben, J. Deslippe, S. G. Louie, J. R. Chelikowsky, Quasiparticle energies and optical excitations of 3C-SiC divacancy from GW and GW plus Bethe-Salpeter equation calculations

Physical Review Materials (Editor Suggestion) 6 (3), 036201, (2022) (Editor's suggestion)

X. Wu#, W. Gao#, J. Chai, C. Ming, M. Chen, H. Zeng, P. Zhang, S. Zhang, Y. Sun, Defect tolerance in chalcogenide perovskite photovoltaic material BaZrS₃,

SCIENCE CHINA Materials, 64 (12), 2976-2986 (2021) 

W. Gao, J. Zhao, J. Chelikowsky, Out-of-plane polarization and topological magnetic vortices in multiferroic CrPSe₃

Physical Review Materials 6 (10), L101402 (2022) (Editor's suggestion)

W. Gao and J. Chelikowsky, Prediction of intrinsic ferroelectricity and strong piezoelectricity in two dimension arsenic chalcogenide

Nano Lett., 20, 11, 8346–8352 (2020)

Y. Tian#, W. Gao#, J. Chelikowsky, L. Yang, Optically Driven Magnetic Phase Transition of Monolayer RuCl₃

Nano Letters 19, 7673-7680 (2019) 

Y Wu, W Xia, W Gao, F Jia, P Zhang, W Ren, Quasiparticle electronic structure of honeycomb C3N: from monolayer to bulk

2D Materials 6 (1), 015018 (2018) 

W. Gao, X. Gao, T. A. Abtew, Y. Sun, S. Zhang, P. Zhang, Quasiparticle band gap of organic-inorganic hybrid perovskites: Crystal structure, spin-orbit coupling, and self-energy effects

Phys. Rev. B 93, 085202 (2016) 

T. A. Abtew, W. Gao, X. Gao, Y. Sun, S. Zhang, and P. Zhang, Theory of Oxygen-Boron Vacancy Defect in Cubic Boron Nitride: A Diamond NV Isoelectronic Center

Phys. Rev. Lett. 113, 136401 (2014)