Topic: Electronic band structure of d- and f-electron systems from the GW perspective

Speaker:Hong Jiang （蒋鸿）

　　　　　College of Chemistry, Peking University

Time: 9：00am,(Monday) July 18,2011

Venue: Room 468,Lee Hsun building

Welcome to attend!

Abstract

The accurate first-principles description of d- and f-electron systems is currently regarded as one of the great challenges in condensed matter physics due to the simultaneous presence of itinerant (delocalized) and highly localized states and interactions between them. Density-functional theory (DFT) in the local-density approximation (LDA) proves to be inadequate for d/f-electron systems due to the severe self-interaction (delocalization) error. The simplest extension that can overcome the major failure of LDA is by introducing a local Hubbard like correction (LDA+U), which, however, treats itinerant states still at the LDA level. Many-body perturbation theory in the GW approach offers both a quasi-particle perspective (appropriate for itinerant states) and an exact treatment of exchange (appropriate for localized states). The combination of GW with LDA+U (GW@LDA+U) is therefore promising for d/f-electron systems. In this talk, I will present a systematic investigation of the GW@LDA+U approach, as implemented in our newly developed all-electron GW code FHI-GAP (Green's function with Augmented Planewaves) [1], for a series of prototypical d- and f-electron systems including later transition metal oxides [2], lanthanide oxides [3] and actinide oxides [4]. We observed good agreement between the GW density of states and experimental spectra using U determined by the constrained DFT approach. All main features found in experimental band gaps of the lanthanide sesquioxide series (Ln₂O₃) are well reproduced by our approach. Consistent with other GW approaches, the satellite structure in the photoemission spectroscopy of late transition metal oxides is still missing, and the binding energy of occupied d/f-states tends to be underestimated. We also compare GW@LDA+U to other variants of GW approaches as well as dynamical mean-field theory to illuminate pros and cons of different approaches. I will also present some recent work on first-principles determination of the Hubbard U.

[1] H. Jiang, R. Gomez-Abal, X. Li, H. Jiang, C. Meisenbichler, C. Ambrosch-Draxl, M. Scheffler, in preparation (2011).

[2] H. Jiang, R. Gomez-Abal, P. Rinke, and M. Scheffler, Phys. Rev. B 82, 045108 (2010)

[3] H. Jiang, R. Gomez-Abal, P. Rinke, and M. Scheffler, Phys. Rev. Lett. 102, 126403 (2009).

[4] H. Jiang, P. Rinke and M. Scheffler, in preparation (2011).

蒋 鸿

研究经历

• 1994.9 - 2003.7: 北京大学化学学院,学士，博士
• 2001.2 - 2004.8: 美国杜克大学化学系和物理系,研究助理
• 2004.10 - 2006.9：德国法兰克福大学，博士后
• 2006.10 - 2008.11：德国柏林Fritz-Haber研究所，博士后
• 2008.12 至今 : 北京大学化学学院特聘研究员

研究兴趣

• 基于格林函数的电子能带结构理论；
• 针对d/f电子材料的第一性原理方法；
• 太阳能转化材料的电子能带结构；
• 分子磁性材料；
• 过渡和稀土元素材料的表面与催化。

代表性论文

1. Hong Jiang, Structural and electronic properties of ZrX₂ and HfX₂ (X=S, and Se) from first principles calculations，J. Chem. Phys. 134, 204705 (2011).

2. Hong Jiang, Ricardo I. Gomez-Abal, Patrick Rinke and Matthias Scheffler, First principles modeling of localized d states with the GW@LDA+U approach, Phys. Rev. B 82 , 045108 (2010).

3. Hong Jiang , Ricardo I. Gomez-Abal, Patrick Rinke and Matthias Scheffler, Localized and itinerant states in lanthanide oxides united by GW@LDA+U , Phys. Rev. Lett. 102, 126403 (2009).

4. Hong Jiang and Eberhard Engel, Random-phase-approximation-based correlation energy functionals: Benchmark results for atoms，J. Chem. Phys. 127, 184108 (2007).

5. Hong Jiang and Eberhard Engel, Second Order Kohn-Sham Perturbation Theory: Correlation Potential for Atoms in a Cavity, J. Chem. Phys. 123, 224102 (2005).

6. Hong Jiang, Harold U. Baranger and Weitao Yang, Spin and Conductance Peak Spacing Distributions in Large Quantum Dots: A Density Functional Theory Study, Phy. Rev. Lett. 90, 026806 (2003).