Prof. Yam Chi Yung visits XMU -能源材料化学协同创新中心

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Prof. Yam Chi Yung visits XMU

The iChEM invited Prof. Yam Chi Yung of Beijing Computational Science Research Center to visit XMU on October 14-18. He will have discussions with our professors and students and also present two lectures as the below:

1. Topic: Quantum Mechanical Simulations of Complex Systems: O(N) TDDFT and QM/EM Method

Time: October 15, 2013 (Tuesday) 4:00 pm

Location: Rm# 202 of Lujiaxi Building

Abstract: The poor scaling of many existing quantum mechanical methods with respect to the system size hinders their applications to large systems. A linear-scaling time-dependent density-functional theory is developed to study excited states of complex molecular systems. Instead of many-body wavefunction, the equation of motion is solved for the reduced single-electron density matrix in the time domain. The time-dependent first-order response of the density matrix due to an external perturbation is solved using Chebyshev method with high efficiency and accuracy. Linear-scaling of CPU time and memory usage with the system size is achieved by exploring the sparsity of the involving matrices as well as by introduction of a cutoff for the first-order density matrix. To further increase the efficiency, a hybrid quantum mechanics/electromagnetics (QM/EM) method is developed to model electronic devices at nanoscale. The whole simulation domain is divided into QM and EM regions and solved in a self-consistent manner between quantum and classical models. Potential distributions and current densities at the interface are exploited as the boundary conditions for information exchange between the two regions. The method is expected to bridge the gap between quantum mechanics simulation and circuit modeling.

2. Topic: Multi-scale Quantum Mechanics/Electromagnetics Method for Device Simulations

Time: October 17, 2013 (Thursday) 4:00 pm

Location: Rm# 202 of Lujiaxi Building

Abstract: The continuous downsizing of modern electronic devices implies the increasing importance of quantum phenomena. As the feature sizes of transistors inch towards 10 nanometer, simulations including quantum effects and atomistic details are inevitable. A novel hybrid quantum mechanics and electromagnetics (QM/EM) method is developed to model individual electronic components at the nanoscale. QM and EM models are solved in different regions of the system in a self-consistent manner. The method is expected to bridge the gap between quantum mechanics calculation and circuit modeling. Based on the simulation results, a compact model is generated for subsequent circuit simulation. Applications of the method to junctionless field-effect transistors and photovoltaic device will be presented.

Welcome to Join us!

Prof. Yam Chi Yung is an Assistant Professor in the Beijing Computational Science Research Center introduced by the well-known 1000 Young Talent Program of China and awarded the Excellent Young Researcher Award by the National Natural Science Foundation of China (NSFC) in 2013. He received his Ph.D degree in Prof. Guanhua Chen’s group of University of Hong Kong (UHK) in 2004, and then had Post-doc with Prof. T. Frauenheim of the Bremen Center for Computational Materials Science at the University of Bremen in 2009. In 2010, He came back to UHK as a research associate professor in the research area of theory, modeling, and simulation of emerging electronics. Prof. Yam’s research focuses on multi-scale approach to simulate nanoelectronics, quantum transport and time-dependent density functional theory for open systems, and linear-scaling quantum mechanical methods for excited states.

Publications:
1) “Linear-Scaling Quantum Mechanical Methods for Excited States”, ChiYung Yam, Qing Zhang, Fan Wang, and GuanHua Chen, Chem. Soc. Rev. 41, 3821 (2012).
2) “Dynamic Multiscale Quantum Mechanics/Electromagnetics Simulation Method", Lingyi Meng, ChiYung Yam, SiuKong Koo, Quan Chen, Ngai Wong and GuanHua Chen, J. Chem. Theory Comput. 8, 1190 (2012).
3) “Multiscale quantum mechanics/electromagnetics simulation for electronic device”, ChiYung Yam, Lingyi Meng, GuanHua Chen, Quan Chen, and Ngai Wong, Phys. Chem. Chem. Phys. 13, 14365 (2011).
4) “Time-dependent density functional theory based Ehrenfest dynamics”, Fan Wang, ChiYung Yam, Lihong Hu, and GuanHua Chen, J. Chem. Phys. 135, 044126 (2011).
5) “Time-dependent density functional theory for quantum transport”, X. Zheng, G.H. Chen, Y. Mo, S.K. Koo. H. Tian, C.Y. Yam and Y.J. Yan, J. Chem. Phys. 133, 114101 (2010).
6) “Theoretical prediction of topological insulators in thallium-based III-V-VI2 ternary chalcogenides”, B.H. Yan, C.X. Liu, H.J. Zhang, C.Y. Yam, X.L. Qi, Th. Frauenheim and S.C. Zhang, Euro. Phys. Lett. 90, 37002 (2010).
7) “Local Vibrational Excitation through Extended Electronic States at a Germanium Surface”, K. Tomatsu, K. Nakatsuji, M. Yamada, F. Komori, B.H. Yan, C.Y. Yam, Th. Frauenheim, Y. Xu, and W.H. Duan, Phys. Rev. Lett. 103, 266102 (2009).
8) “Dynamic admittance of carbon nanotube-based molecular electronic devices and their equivalent circuit”, C.Y. Yam, Y. Mo, F. Wang, X.B. Li, G.H. Chen, X. Zheng, Y. Matsuda, J. Tahir-Kheli and W.A. Goddard III, Nanotechnology 19, 495203 (2008).
9) “Linear scaling time-dependent density-functional tight-binding method for absorption spectra of large systems”, F. Wang, C.Y. Yam, G.H. Chen, X.J. Wang, K.N. Fan, T.A. Niehaus and Th. Frauenheim, Phys. Rev. B 76, 045114 (2007).
10) “Time-dependent density-functional theory for open systems”, X. Zheng, F. Wang, C.Y. Yam, M. Yan and G.H. Chen, Phys. Rev. B 75, 195122 (2007).
11) “Electronic structure and charge distribution of potassium iodide intercalated single-walled carbon nanotubes”, C.Y. Yam, C.C. Ma, X.J. Wang and G.H. Chen, App. Phys. Lett. 85, 4484 (2004).
12) “Linear-scaling time-dependent density functional theory”, C.Y. Yam, S. Yokojima and G.H. Chen, Phys. Rev. B 68, 153105 (2003).

发布日期:2013/10/14 发布者: 点击数:【打印】