• Stand-alone NLO code interfaced with VASP & Quantum-ESPRESSO

• Highly parallelized and benchmarked on 10s to 1000s cores

• Support second harmonic generation and nonlinear photocurrent

• Support tensor symmetrization

• Support SHG calculations with and without spin-orbit coupling

• Under extensive development for efficient & accurate NLO calculations

• Hua Wang and Xiaofeng Qian, Giant Optical Second Harmonic Generation in Two-Dimensional Multiferroics. Nano Letters 17, 5027-5034 (2017).

• Hua Wang and Xiaofeng Qian. Ferroicity-driven nonlinear photocurrent switching in time-reversal invariant ferroic materials. Science Advances 5, eaav9743 (2019).

• Hua Wang and Xiaofeng Qian. Ferroelectric nonlinear anomalous Hall effect in few-layer WTe2. npj Computational Materials 5, 119 (2019).

• Jun Xiao, Ying Wang, Hua Wang, C. D. Pemmaraju, Siqi Wang, Philipp Muscher, Edbert J. Sie, Clara M. Nyby, Thomas P. Devereaux, Xiaofeng Qian, Xiang Zhang, and Aaron M. Lindenberg. Berry curvature memory through electrically driven stacking transitions. Nature Physics 16, 1028-1034 (2020).

• Mohammad Taghinejad, Zihao Xu, Hua Wang, Hossein Taghinejad, Kyu-Tae Lee, Sean P. Rodrigues, Ali Adibi, Xiaofeng Qian, Tianquan Lian, and Wenshan Cai. Photocarrier-Induced Active Control of Second-Order Optical Nonlinearity in Monolayer MoS2. Small 16, 1906347 (2020).

• Jia Liang, Qiyi Fang, Hua Wang, Rui Xu, Shuai Jia, Yuxuan Guan, Qing Ai, Guanhui Gao, Hua Guo, Kaijun Shen, Xiewen Wen, Tanguy Terlier, Gary P. Wiederrecht, Xiaofeng Qian, Hanyu Zhu, and Jun Lou. Perovskite‐Derivative Valleytronics. Advanced Materials 32, 2004111 (2020).

• Hua Wang and Xiaofeng Qian. Electrically and magnetically switchable nonlinear photocurrent in РТ-symmetric magnetic topological quantum materials. npj Computational Materials 6, 199 (2020).

• Zhuoliang Ni, Amanda V. Haglund, Hua Wang, Bing Xu, Christian Bernhard, David G. Mandrus, Xiaofeng Qian, Eugene J. Mele, Charles L. Kane, and Liang Wu. Imaging the Néel vector switching in the monolayer antiferromagnet MnPSe3 with strain-controlled Ising order. Nature Nanotechnology 16, 782–787 (2021).

• Alex Strasser, Hua Wang, and Xiaofeng Qian. Nonlinear Optical and Photocurrent Responses in Janus MoSSe Monolayer and MoS2–MoSSe van der Waals Heterostructure. Nano Letters 22, 4145–4152 (2022).

• Efficient and Equivariant Graph Networks for Predicting Quantum Hamiltonian

• Accelerate self-consistent electronic structure calculations with QHNet-predicted Hamiltonian

QHNet on GitHub 

• Haiyang Yu, Zhao Xu, Xiaofeng Qian, Xiaoning Qian, and Shuiwang Ji. Efficient and Equivariant Graph Networks for Predicting Quantum Hamiltonian. Proceedings of the 40th International Conference on Machine Learning, PMLR 202, 40412-40424 (2023). arXiv Preprint:2306.04922 (2023)

• Quantum Hamiltonian Database with 130,831 molecules and 999 MD trajactories

QH9 on GitHub 

• Haiyang Yu, Meng Liu, Youzhi Luo, Alex Strasser, Xiaofeng Qian, Xiaoning Qian, and Shuiwang Ji. QH9: A Quantum Hamiltonian Prediction Benchmark for QM9 Molecules. Conference on Neural Information Processing Systems (NeurIPS), Track on Datasets and Benchmarks, accepted (2023). arXiv Preprint:2306.09549 (2023)

• Highly localized QOs by Bloch subspace optimization

• Exactly reproduce low-energy first-principles electronic structure

• Efficient calculations of 3D Fermi surface, DOS, PDOS

• Mulliken charge and bond order analysis for solids/surfaces/molecules

• Support NCPP, USPP and PAW

• Support point group symmetry for Bloch wave functions

• Support spin-unpolarized, spin-polarized, and spin-orbit coupling

• Generate real-space representation of localized QOs

• Generate tight-binding Hamiltonian in the QO basis

• Generate XCrySDen XSF/BXSF files for structures, QOs, and Fermi surfaces

• Interface with various DFT packages

QO for Quantum-ESPRESSO 4.x

• Xiaofeng Qian, Ju Li, Liang Qi, Cai-Zhuang Wang, Tzu-Liang Chan, Yong-Xin Yao, Kai-Ming Ho, and Sidney Yip. Quasiatomic orbitals for ab initio tight-binding analysis. Physical Review B 78, 245112 (2008).

• Tzu-Liang Chan, Yong-Xin Yao, Cai-Zhuang Wang, Wen-Cai Lu, Ju Li, Xiaofeng Qian, Sidney Yip, and Kai-Ming Ho. Highly localized quasiatomic minimal basis orbitals for mo from ab initio calculations. Physical Review B 76, 205119 (2007)

• Xiaofeng Qian, Junwei Liu, Liang Fu, and Ju Li. Quantum spin Hall effect in two-dimensional transition metal dichalcogenides. Science 346, 1344-1347 (2014). 

• Daniel A. Rhodes, Apoorv Jindal, Noah F. Q. Yuan, Younghun Jung, Abhinandan Antony, Hua Wang, Bumho Kim, Yu-che Chiu, Takashi Taniguchi, Kenji Watanabe, Katayun Barmak, Luis Balicas, Cory R. Dean, Xiaofeng Qian, Liang Fu, Abhay N. Pasupathy, and James Hone. Enhanced Superconductivity in Monolayer Td-MoTe2. Nano Letters 21, 2505–2511 (2021)

• Jian Tang, Thomas Siyuan Ding, Hongyu Chen, Anyuan Gao, Tiema Qian, Zumeng Huang, Zhe Sun, Xin Han, Alex Strasser, Jiangxu Li, Michael Geiwitz, Mohamed Shehabeldin, Vsevolod Belosevich, Zihan Wang, Yiping Wang, Kenji Watanabe, Takashi Taniguchi, David C. Bell, Ziqiang Wang, Liang Fu, Yang Zhang, Xiaofeng Qian, Kenneth S. Burch, Youguo Shi, Ni Ni, Guoqing Chang, Su-Yang Xu, and Qiong Ma. Dual quantum spin Hall insulator by density-tuned correlations in TaIrTe4. Nature 628, 515–521 (2024).

• Interfaces to plane-wave DFT codes: including VASP, Dacapo, and PWscf (PW in Quantum-Espresso package) using norm conserving and ultrasoft pseudopotentials and PAW method

• QO module: construct highly localized QOs to reproduce electronic structure obtained from high-quality DFT planewave calculations up to a few eVs above the Fermi level; provide real-space QOs and their tight-binding Hamiltonian and overlap matrices, Mulliken and Lowdin charge analysis, (QO-projected) band structure and density of states, (energy/velocity/mass-resolved) Fermi surface for both spin-collinear and spin-noncollinear systems (with and without spin-orbit coupling)

• NEGF module: calculate phase-coherent quantum transport using non-equilibrium Green's function method in the QO basis-set together with density of states and conductance eigenchannel analysis

• GW/TDDFT module: calculate quasiparticle electronic structure and optical excitations using many-body perturbation theory in Hedin's GW approximation and time-dependent density-functional theory (TDDFT) in the QO basis-set (in development)

• Visualization module: visualize volumetric data including QOs, conductance eigenchannels, and Fermi surface using VTK and POV-Ray, and atomistic structure using AtomEye and XCrySDen

• Data flow: in the convenient NetCDF/HDF5 format

• Xiaofeng Qian, Ju Li, and Sidney Yip. Calculating phase-coherent quantum transport in nanoelectronics with ab initio quasiatomic orbital basis set. Physical Review B 82, 195442 (2010).

• Support Vanderbilt ultrasoft pseudopotentials

• Optical absorption spectrum from real-time propagation method

• Real-time dynamics of electron transport through nanoscale junctions

RT-TDDFT for Quantum ESPRESSO   (Implemented by Xiaofeng Qian and Davide Ceresoli)

• Xiaofeng Qian, Ju Li, Xi Lin, and Sidney Yip. Time-dependent density functional theory with ultrasoft pseudopotentials: Real-time electron propagation across a molecular junction. Physical Review B 73, 035408 (2006).

• Project lead by Professor Paolo Umari at University of Padova, Italy, et al.

• Calculate quasiparticle energies at the GW level

• Provide efficient representation of polarizability through Wannier function construction and product reduction

• Suitable for large molecular and solid-state systems

GWW for Quantum ESPRESSO

• Paolo Umari, Geoffrey Stenuit, and Stefano Baroni. Optimal representation of the polarization propagator for large-scale GW calculations. Physical Review B 79, 201104(R) (2009).

• Paolo Umari, Geoffrey Stenuit, and Stefano Baroni. GW quasiparticle spectra from occupied states only. Physical Review B 85, 115104 (2010).

• Paolo Umari, Xiaofeng Qian, Nicola Marzari, Geoffrey Stenuit, Luigi Giacomazzi, and Stefano Baroni. Accelerating GW calculations with optimal polarizability basis. Physica Status Solidi B 248, 527-536 (2011).

• Xiaofeng Qian, Paolo Umari, and Nicola Marzari. Photoelectron properties of DNA and RNA bases from many-body perturbation theory. Physical Review B 84, 075103 (2011).

• Xiaofeng Qian, Paolo Umari, and Nicola Marzari. First-principles investigation of organic photovoltaic materials C60, C70, [C60]PCBM, and bis-[C60]PCBM using a many-body G0W0-Lanczos approach. Physical Review B 91, 245105 (2015).