购彩中心

TOPIC：Crystal structure determination using electron diffraction tomography 
SPEAKER：Dr. Peter Oleynikov，Stockholm University
TIME：July 5 (Tuesday) PM15:00 
LOCATION：Room 528, Chemistry Building A (化学A楼528演讲厅)
INVITER：A.Prof. Lu Han (韩璐特别研究员)

16:00，在透射电镜室（化学A楼107室）进行演示

Abstract：

A new method of quantitative three-dimensional reciprocal space scanning using automated 3D electron diffraction tomography (EDT) is developed [1]. The method allows the collection of 3D data by sweeping reciprocal space in the range from ‑43° to +43° (double tilt holder) or from ‑72° to +72° using a single ultra-high tilt holder and produces ~2000 frames/hour. The collected data of high quality can be used for further determination of a 3D crystal structure. Several known (for example, EMM-8 and ETS-10, Fig. 1 left, and etc.) and unknown structures have been successively solved using the 3D EDT method. The important outcome from the structure solution is that the lightest atoms (e.g. oxygen) can be easily identified in the calculated potential maps obtained during the structure solution using the 3D intensities extracted from the EDT datasets. Scanning reciprocal space using EDT allows registering not only the reflections, but also the 3D diffuse scattering intensity around diffraction spots which can be related to defects and stacking faults. Many zeolites and microporous compounds have a lot of defects due to the nature of their crystal structure. One of the representatives in the microporous titanosilicates family is ETS-10 with a framework that contains −Ti−O−Ti−O− chains and has three-dimensional 12-ring pore system with straight pores and pores that are bent due to the faulting [2]. Strong diffuse scattering was observed in the ED pattern frames due to extensive faults present in this material. From the reconstructed 3D reciprocal space we were able to conclude that the diffuse streaks appear only in the direction of the c* axis. Another important area of application of the 3D EDT technique is the combination of the electron diffraction data together with high resolution images which was successfully applied in the solution of the most complex zeolite ITQ-39 [3] (Fig 1, right).  

Fig. 1. Left: ETS-10 reciprocal space view. Right: ITQ-39 crystal structure.

References:

(1)  Zhang, D., Oleynikov, P., Hovmöller, S. & Zou, X.D. (2010). Z. Kristallogr. 225, 94-102.

(2) Anderson, M.W., Terasaki, O., Ohsuna, T., Philippou, A., MacKay, S.P., Ferreira, A., Rocha, J. & Lidin, S. (1994). Nature. 367, 347-351.

(3) Willhammar, T., Sun, J.L., Wan, W., Oleynikov, P., Zhang, D.L., Zou, X.D., Moliner, M., Gonzalez, J., Martínez, C., Rey, F. & Corma, A. (2012). Nature Chemistry. 4, 188-194.

Peter Oleynikov

Peter Oleynikov has graduated from the Materials Sciences Department, Moscow State University. During his PhD at Stockholm University he worked in the field of electron crystallography focused on texture patterns and precession electron diffraction analysis. From September 2006 to April 2008 he completed his post-doctoral employment at the Brookhaven National Laboratory, Center for Functional Nanomaterials. Since January 2012 Peter has been employed as assistant professor at the department of Materials and Environmental Chemistry of Stockholm University where he solely developed the electron diffraction tomography method (3D EDT) for the acquisition of 3D electron diffraction data from single sub-µm sized crystals and the data processing algorithms of the 3D EDT data sets.

Simultaneously Peter has developed and maintained several software packages for the data processing of electron diffraction patterns, high resolution images, dynamical refinement and simulation softwares that are widely used in the field of electron microscopy.