Invited Speaker：Prof. Lin-Wang Wang

Introduction：

Dr. Lin-Wang Wang is a senior staff scientist at Lawrence Berkeley National Laboratory, Berkeley, CA, U.S.  Dr. Wang has 25 years of experience in large scale electronic structure calculations. He has worked in O(N) electronic structure calculations in early 1990s. He invented the folded spectrum method which pushed the limit of nonselfconsistent electronic structure calculations from 100 atoms to thousands of atoms. He developed a linear combination of bulk bands (LCBB) method for semiconductor heterostructrure electronic structure calculations, which allows the calculation of  million atom devices. He developed generalized moments method which calculates the density of state and optical absorption spectra of a given system without explicit calculation of its eigenstates. He also developed a popular parallel total energy plane wave pseudopotential program (PEtot). He invented a charge patching method, which enables the ab initio accuracy thousand atom calculations for nanosystems. He has developed a linear scaling three dimensional fragment method (LS3DF), which can be used to selfconsistently calculate systems with tens of thousands of atoms. Recently, he developed a new algorithm for real-time time-dependent DFT calculations which accelerates the traditional algorithms by hundreds of times. He has published 280 SCI papers with about 20,000 citations, and an h-index of 61. 

【Lecture Title】Linear scaling methods to calculate large size nanosystems

Time: 09:30-11:00 am, August 2nd, 2017

Location: New MSE Building, No. 01 Meeting Room

Abstract: First principle quantum mechanical simulation has become a major part of material science research. However, it is particularly challenging to simulate nanosystems due to their relatively large sizes (e.g., > 1000 atoms). In this talk, I will present several of our linear scaling methods to calculate such nanosystems. We have studied the optical properties of colloidal nanocrystals, the results reveal some subtle dependences on the geometries and heterostructures of the nanocrystals. We have also investigated the surface passivations of the nanocrystals. This gives us a much deeper understanding of the surface chemistry and why the quantum dots are optically robust. Finally, I will also show our results on the hybrid perovskite material for solar cell. I will show how the carrier wave function in that system is localized by the organic molecule orientation fluctuation, and how such fluctuation will affect the carrier mobility in the system.