我们团队创立了普适性的高等级密度泛函理论框架：XYG3型双杂化泛函方法（xDH）。我们超越主流杂化框架，从绝热路径和微扰理论出发，提出了双杂化泛函 XYG3。XYG3 采用了一类独创的构造框架：它用一个低阶泛函产生密度，另一个高阶泛函计算能量，这样既保证了效率又保证了精度。XYG3 型泛函(统称为 xDH)以比高等级波函数方法 CCSD(T)低 2-4个数量级的计算消耗，在热力学(如反应热)、动力学(如反应能垒)和弱相互作用(如范德华作用)等各方面，均达到了与之相媲美的计算精度。xDH 双杂化理论框架已经成为量化领域内开发高精度计算方法的重要范式，引领了一批代表目前最高精度的泛函发展。除我们团队随后提出的 XYGJ-OS、XYG7外，美国科学院院士 Head-Gordon 教授的 ωB97M(2) ，以及国际量子分子科学院院士 Martin教授的 xrevDS等均明确表明是按 xDH 框架构造的。围绕xDH方法，我们开发出 高精度性质计算系列新方法，突破了高等级方法一般只能进行单点能量计算的局限，建立了完善的 xDH 理论框架。实现了其电子密度计算新功能，证实了 xDH 是目前唯一能够保证能量和密度同时正确的优异泛函；建立了 xDH 的解析梯度新理论，实现了精确、高效的分子结构自动优化；实现了双杂化泛函谱学性质的解析计算，与 CCSD(T)结果高度吻合(如频率计算平均误差小于 20 波数，13C 化学位移计算精度达 1 ppm)；极大地提高了 DFT轨道能对电离能、电子亲合能和带宽的描述精度，为重要化学概念(如电负性、硬软度等)的定量刻画提供了新手段。

1. Wenjie Yan and Xin Xu*, ‘Accurate Prediction of Nuclear Magnetic Resonance Parameters via the XYG3 Type of Doubly Hybrid Density Functionals’, J. Chem. Theory Comput., 2022, 18(5) 2931-2946. DOI:10.1021/acs.jctc.2c00055.

2. Wenjie Yan and Xin Xu*, ‘Analytic Gradients for Long-Range-Corrected XYG3 type of Doubly Hybrid Density Functionals: Theory, Implementation and Assessment’, J. Phys. Chem.A, 2022, 126(24) 3937-3946.DOI:10.1021/acs.jpca.2c01962.

3. Andrew M. Teale, Trygve Helgaker, Andreas Savin, Carlo Adamo, Bálint Aradi, Alexei V. Arbuznikov, Paul W. Ayers, Evert Jan Baerends, Vincenzo Barone, Patrizia Calaminici, Eric Cancès, Emily A. Carter, Pratim Kumar Chattaraj, Henry Chermette, Ilaria Ciofini, T. Daniel Crawford, Frank De Proft, John F. Dobson, Claudia Draxl, Thomas Frauenheim, Emmanuel Fromager, Patricio Fuentealba, Laura Gagliardi, Giulia Galli, Jiali Gao, Paul Geerlings, Nikitas Gidopoulos, Peter M. W. Gill, Paola Gori-Giorgi, Andreas Görling, Tim Gould, Stefan Grimme, Oleg Gritsenko, Hans Jørgen Aagaard Jensen, Erin R. Johnson, Robert O. Jones, Martin Kaupp, Andreas M. Köster, Leeor Kronik, Anna I. Krylov, Simen Kvaal, Andre Laestadius, Mel Levy, Mathieu Lewin, Shubin Liu, Pierre-François Loos, Neepa T. Maitra, Frank Neese, John P. Perdew, Katarzyna Pernal, Pascal Pernot, Piotr Piecuch, Elisa Rebolini, Lucia Reining, Pina Romaniello, Adrienn Ruzsinszky, Dennis R. Salahub, Matthias Scheffler, Peter Schwerdtfeger, Viktor N. Staroverov, Jianwei Sun, Erik Tellgren, David J. Tozer, Samuel B. Trickey, Carsten A. Ullrich, Alberto Vela, Giovanni Vignale, Tomasz A.Wesolowski, Weitao Yang, Xin Xu ‘DFT Exchange: Sharing Perspectives on the Workhorse of Quantum Chemistry and Materials Science’,Phys. Chem. Chem.Phys., 2022, 24,28700-28781. DOI: 10.1039/d2cp02827a.

4. Yizhen Wang, Yajing Li, Jun Chen, Igor Ying Zhang*, Xin Xu*, 'Doubly hybrid functionals close to chemical accuracy for both finite and extended systems: Implementation and test of XYG3 and XYGJ-OS', JACS Au, 2021, 1 (5): 543-549. DOI: 10.1021/jacsau.1c00011.

5. Igor Ying Zhang*, Xin Xu*, 'Exploring the limits of the XYG3-type doubly hybrid approximations for the main-group chemistry: The xDH@B3LYP model', J. Phys. Chem. Lett., 2021, 12 (10): 2638-2644. DOI: 10.1021/acs.jpclett.1c00360.

6. Igor Ying Zhang*, Xin Xu*, ‘On the Top Rung of Jacob’s Ladder of Density Functional Theory: Toward Resolving the Dilemma of SIE and NCE’, WIREs Comput. Mol. Sci., 2021, 11, e1490. DOI: 10.1002/wcms.1490.

7. Ruoxin Zheng, Igor Ying Zhang,* Xin Xu, 'Development and benchmark of lower scaling doubly hybrid density functional XYG3', Chem. J. Chin. Univ.-Chin., 2021, 42(7), 2210-2217. DOI:10.7503/cjcu20210308.

8. Yonghao Gu, Xin Xu*, ‘Extended Koopmans’ Theorem in the Adiabatic Connection Formalism: Applied to Doubly Hybrid Density Functionals’, J. Chem. Phys., 2020, 153, 044109. DOI: 10.1063/5.0010743.

9. Neil Qiang Su, Zhenyu Zhu, Xin Xu*, ‘Doubly Hybrid Density Functionals That Correctly Describe Both Density and Energy for Atoms’, Proc. Natl. Acad. Sci. U.S.A., 2018, 115(10), 2287-2292. DOI: 10.1073/pnas.1713047115.

10. Neil Qiang Su, Xin Xu*, ‘Development of New DFT Functionals’, Annu. Rev. Phys. Chem., 2017, 68, 155-182. DOI: 10.1146/annurev- physchem-052516-044835 (invited contribution)

11. Neil Qiang Su, Xin Xu*, ‘The XYG3 Type of Doubly Hybrid Functionals’, WIREs Comput. Mol. Sci., 2016, 6, 721-747. DOI: 10.1002/wcms.1274. (invited contribution)

12. Neil Qiang Su, Xin Xu*, ‘Second-Order Perturbation Theory for Fractional Occupation Systems: Applications to Ionization Potential and Electron Affinity Calculations’, J. Chem. Theory Comput., 2016, 12(5), 2285-2297. DOI: 10.1021/acs.jctc.6b00197.

13. Neil Qiang Su, Xin Xu*, ‘A Comparative Study of xDH-PBE0 and DSD-PBEPBE-D3BJ Functionals’, Mol. Phys., 2016, 114(7-8), 1207-1217. DOI: 10.1080/00268976.2015.1129462.

14. Eric Bremond, Marika Savarese, Neil Qiang Su, Ángel Pérez-Jiménez, Xin Xu, Carlo Adamo*, ‘Benchmarking Density-Functionals on Molecular Structural Parameters’, J. Chem. Theory Comput., 2016, 12, 459-465. DOI: 10.1021/acs.jctc.5b01144.

15. Neil Qiang Su, Xin Xu*, ‘Beyond Energies: Geometry Predictions with the XYG3 Type of Doubly Hybrid Density Functionals’, Chem. Commun., 2016, 52(96), 13840-13860. DOI: 10.1039/C6CC04886B. (Feature Article, invited contribution)

16. Neil Qiang Su, Xin Xu*, ‘Towards the Construction of Parameter-Free Doubly Hybrid Density Functionals’, Int. J. Quantum Chem., 2015, 115, 589-595, DOI: 10.1002/qua.24849. (Perspective)

17. Neil Qiang Su, Xin Xu*, ‘Integration Approach at the Second-Order Perturbation Theory: Applications to Ionization Potential and Electron Affinity Calculations’, J. Chem. Theory Comput., 2015, 11(10), 4677-4688. DOI: 10.1021/acs.jctc.5b00591.

18. Igor Ying Zhang, Neil Qiang Su, Éric A. G. Brémond, Carlo Adamo, Xin Xu*, ‘Reply to “Comment on “Doubly Hybrid Density Functional xDH-PBE0 from a Parameter-Free Global Hybrid Model PBE0”” [J. Chem. Phys. 143, 187101 (2015)]’, J. Chem. Phys., 2015, 143(18), 187102. DOI: 10.1063/1.4934820.

19.  I. Y. Zhang and X. Xu, A New-Generation Density Functional Towards Chemical Accuracy for Chemistry of Main Group Elements, SpringerBriefs in Molecular Science, Springer Heidelberg, 2014, ISBN 978-3-642-40420-7, DOI 10.1007/978-3-642-40421-4

20. Neil Qiang Su, Weitao Yang, Paula Mori-Sánchez, Xin Xu*, ‘Fractional Charge Behavior and Band Gap Predictions with the XYG3 Type of Doubly Hybrid Density Functionals’, J. Phys. Chem. A, 2014, 118(39), 9201-9211. DOI: 10.1021/jp5029992.

21. Neil Qiang Su, Xin Xu*, ‘Error Accumulations in Adhesive Energies of Dihydrogen Molecular Chains: Performances of the XYG3 Type of Doubly Hybrid Density Functionals’, J. Phys. Chem. A, 2014, 119(9), 1590-1599, DOI: 10.1021/jp507711t.

22. Igor Ying Zhang, Jun Jiang, Bin Gao, Xin Xu*, Yi Luo*, ‘RRS-PBC: A Molecular Approach for Periodic Systems’, Sci. China, Ser. B, 2014, 57, 1399-1404. (Special issue of Jean-Marie Andre’s 70th anniversary)

23. Neil Qiang Su, Xin Xu*, ‘Construction of a Parameter-Free Doubly Hybrid Density Functional from Adiabatic Connection’, J. Chem. Phys. A, 2014, 140(18), 18A512. DOI: 10.1063/1.4866457.(Invited contribution for DFT50)

24. Neil Qiang Su, Igor Ying Zhang, Xin Xu*, ‘Analytic Derivatives for the XYG3 Type of Doubly Hybrid Density Functionals: Theory, Implementation, and Assessment’, J. Comput. Chem., 2013, 34(20), 1759-1774. DOI: 10.1002/jcc.23312.

25. Neil Qiang Su, Carlo Adamo, Xin Xu*, ‘A Comparison of Geometric Parameters from the PBE-Based Doubly Hybrid Density Functionals PBE0-DH, PBE0-2 and xDH-PBE0’, J. Chem. Phys., 2013, 139(17), 174106. DOI: 10.1063/1.4827024.

26. Neil Qiang Su, Xin Xu*, ‘Recent Progress of the XYG3 Type of Doubly Hybrid Functionals: From Energy Calculations to Analytic Geometry Optimizations’, Sci. Sin. Chim., 2013, 43(12), 1761-1779. DOI: 10.1360/032013-258. (in Chinese)

27. Igor Ying Zhang, Xin Xu*, ‘XYG3 and XYGJ-OS Performances for Noncovalent Binding Energies Relevant to Biomolecular Structures’, 2012, 14(36), 12554-12570. DOI: 10.1039/C2CP40904F. (invited contribution, themed issue: Theoretical chemical physics of biological systems)

28. Igor Ying Zhang, Jianming Wu, Xin Xu*, ‘Extending the Reliability and Applicability of B3LYP’, Chem. Commun., 2010, 46(18), 3057-3070. DOI: 10.1039/C000677G.

29. Ying Zhang, Xin Xu*, William A. Goddard III*, ‘Doubly Hybrid Density Functional for Accurate Descriptions of Nonbond Interactions, Thermochemistry, and Thermochemical Kinetics’, Proc. Nat. Acad. Sci. U.S.A., 2009, 106(13), 4963-4968. DOI: 10.1073/pnas.0901093106.

30. Xin Xu*, Qingsong Zhang, Richard P. Muller, William A. Goddard III* ‘An Extended Hybrid Density Functional (X3LYP) with Improved Descriptions of Nonbond Interactions and Thermodynamic Properties of Molecular Systems’, J. Chem. Phys., 2005, 122(1), 014105. DOI: 10.1063/1.1812257.

31. Xin Xu*, William A. Goddard III*,‘Assessment of Handy-Cohen Optimized Exchange Density Functional (OPTX)’, J. Phys. Chem. A, 2004, 108(40), 8495-8504. DOI: 10.1021/jp047428v.

32. Xin Xu, William A. Goddard III*, ‘The X3LYP Extended Density Functional for Accurate Descriptions of Nonbond Interactions (London Forces, Electrostatics, and Hydrogen Bonding), Spin States, and Thermochemical Properties’, Proc. Natl. Acad. Sci. U.S.A., 2004, 101(9), 2673-2677. DOI: 10.1073/pnas.0308730100.

33. Xin Xu*, William A. Goddard III*, ‘The Extended Perdew-Burke-Ernzerhof Functional with Improved Accuracy for Thermodynamic and Electronic Properties of Molecular Systems’, J. Chem. Phys., 2004, 121(9), 4068-4087. DOI: 10.1063/1.1771632.