My major research interests are theory and simulations of traditional X-ray spectroscopy (XAS, XES, XPS, XPS shake-up, RIXS) and ultrafast nonlinear X-ray spectroscopy (stimulated Raman, four-wave-mixing, etc). The work is carried out by combing quantum chemistry, solid state physics, molecular dynamics, and nonlinear optics. I aim to use the best available electron structure and dynamical methods in spectroscopy studies. The theoretical work aims not only to explain the experimental results, but also to suggest new time-resolved nonlinear x-ray experiments for x-ray free electron (XFEL) facilities. I develop in-house codes for spectroscopic calculations at the density functional theory and multi-configurational levels, taking advantage of the integrals and wave functions read from common quantum chemistry softwares.
o A. Ultrafast nonlinear X-ray Spectroscopy
We design and simulate new ultrafast nonlinear x-ray signals. We use stimulated Raman x-ray spectroscopy to monitor photo-incdued chemical reactions, especially the non adiabatic dynamics near the conical intersections, and other ultrafast chemical processes like charge transfer and charge migration. The correlation between atoms inside a molecule is captured in four-wave-mixing signals.
o B. X-ray Spectroscopy of Nano-materials
Our focus is to use x-ray to characterise the structures of new and important nano materials, especially the 2D materials and molecule-surface interface. We consider large enough models to best reflect the realistic systems, and consider the intrinsic (e.g. vibronic coupling) and environmental (solvent, intermolecular hydrogen bond, stacking) effects to best approach the real physics.
o C. X-ray Spectroscopy of Bio-molecules
Transitional metals are good targets in enzymes (and other related magnetic and energy materials). The focus is the metal L-edge spectroscopy (excitations from 2p orbitals), as the 2p-> 3d transitions capture the bonding, spin, valence around the metal centre. The simulation is however more challenging than the K-edge spectra (excitations from 1s orbitals) due to the multiplet and other effects.
o D. Previous research experience and other interests
I had received solid training in quantum chemistry during my early research carrier. I was involved in a wide arrange of subjects and active in cooperations with scientists in Europe, US, China, Japan, and India via my supervisors. Selected other research topics include:
. Development of fragment-based linear-scaling quantum chemistry method for large molecules
. Monte Carlo and molecular dynamics simulations of solutions and complexes systems
. Nonlinear optical spectroscopy of molecular junctions
. Model Hamiltonian and simulation for single molecular magnets
. Structures and energies of large water clusters isolated or in cages
. Coding of the multi-reference block correlated coupled cluster method
o 2007-2011, PhD in Biotechnology (theoretical chemistry direction), Department of theoretical Chemistry, School of Biotechnology, KTH Royal Institute of Technology, Sweden.
Supervisor: Prof. Yi Luo
Thesis: Structure and spectroscopy of bio- and nano-materials from first-principles simulations.
o 2004-2010, PhD in Chemistry (theoretical chemistry direction), Institute of Theoretical and Computational Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, China.
Supervisor: Prof. Shuhua Li
Thesis: Approximate methods for calculating ground-state electronic structure and properties of large molecules: methodological developments and applications.o 2000-2004, B.S. in Chemistry, School of Chemistry and Chemical Engineering, Nanjing University.
In 2000-2002 also selected in School of Intensitive Instructions for Sciences and Arts (now named Kuang Yaming Hornors School) of the same university for intensive training in math and physics.
Undergraduate thesis: Monte Carlo simulations of polymer configurations in dilute solution (supervised by Profs. Shuhua Li and Jing Ma)
o 1997-2000, Rudong High School, Jiangsu, China
o PostDoc with Prof. Shaul Mukamel, Department of Chemistry, School of Physical Sciences, Universty of California, Irvine, USA, 2013.4-2015.4
o PostDoc with Prof. Yi Luo, Royal Institute of Technology, Sweden, 2011.5-2013.3
2016-2019 Research grant "Dynamics of x-ray-matter interaction with free-electron laser applications" from Swedish Research Council (2015-04510), co-PI.
2012 Research grant for individual researchers ``First-Principles Simulation of L-edge XAS of Fe(II) Spin Crossover Complexes'' from Lars Hierta memorial foundation (Stiftelsen Lars Hiertas Minne), Sweden (FO2012-1039).
A) Ultrafast Nonlinear X-ray Spectroscopy
 Study of double core hole excitations in molecules by X-ray double-quantum-coherence signals: a multi-configuration simulation,
W. Hua, K. Bennett, Y. Zhang, Y. Luo, S. Mukamel, Chem. Sci., 2016, 7, 5922-5933
 Monitoring conical intersections in the ring opening of furan by Attosecond Stimulated X-ray Raman Spectroscopy,W. Hua#, S. Oesterling#, J. D. Biggs, Y. Zhang, H. Ando, R. de Vivie-Riedle, B. P. Fingerhut, and Shaul Mukamel, Struct. Dyna. 2016, 3, 023601. (# equal contribution) (invited article)
W. Hua, J. D. Biggs, Y. Zhang, D. Healion, H. Ren, S. Mukamel, J. Chem. Theory Comput. 2013, 9, 5479–5489
 Nonlinear Spectroscopy of Core and Valence Excitations Using Short X-ray Pulses: Simulation Challenges,
Y. Zhang, W. Hua, K. Bennett, and S. Mukamel, Top. Curr. Chem., 2016, 368, 273-345. (REVIEW).
K. Bennett, Y. Zhang, M. Kowalewski, W. Hua, S. Mukamel*, Phys. Scr., 2016, T169, 014002 (Nobel Symposium Topical Issue: Free electron laser research, REVIEW)
[Highlighted on the journal homepage as Paper of the Week (week 32, 2016)].
B) Transition Metal L-edge X-ray spectroscopy
W Hua, G Tian, G Fronzoni, X Li, M Stener, Y Luo, J. Phys. Chem. A, 2013, 117, 14075–14085
C) X-ray Spectroscopy of Large Systems
X. Li , W. Hua*, B.-Y. Wang , W.-F. Pong , P. -A. Glans , J. Guo* , Yi Luo, Appl. Phys. Lett., 2016, 109, 081601
 Electronic structure of nitrogen doped graphenes in the ground and core-excited states from first-principles simulations
X. Li, W. Hua*, J. Guo, Y. Luo, J. Phys. Chem. C 2015, 119, 16660.
W. Hua, Y. J. Ai, B. Gao, H. Li, H. Ågren, and Y. Luo, Phys. Chem. Chem. Phys. 2012, 14, 9666.
X. Song, W. Hua*, Y. Ma, C. Wang, and Y. Luo, J. Phys. Chem. C 2012,
W. Hua, B. Gao, and Y. Luo, Prog. Chem. 2012, 24, 964 (REVIEW).
W Hua, B Gao, S Li, H Ågren, Y Luo, Phys. Rev. B 2010, 82, 155443.
 Refinement of DNA structures through NEXAFS analysis: applications on guanine and cytosine nucleobases, nucleosides and nucleotides,
W. Hua, B. Gao, S Li, H. Ågren, Y. Luo, J. Phys. Chem. B 2010, 114, 13214.
 Systematic study of soft-X-ray spectra of poly(dG).poly(dC) and poly(dA).poly(dT) DNA duplexes,
D) Development of Fragment-Based Quantum Chemistry Methods
W. Hua, T. Fang, W. Li, J. G. Yu, S. Li, J. Phys. Chem. A 2008, 112, 10864.
E) Molecular Dynamics and Monte Carlo Simulations for Complex Systems
 Understanding the influence of the guest-host interaction on the conformations of short peptides in the hydrophobic cavity: A computational study,
W. Hua, L. Xu, Y. Luo, S. Li, ChemPhysChem 2011, 12, 1325.