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Seminars & Lectures

* TITLE

Probing crystal defects by their vibration modes

* SPEAKERS

Name	Affiliation	E-mail
Prof. Sukit Limpijumnong	Suranaree University of Techonology and Synchrotron Light Research Institute, Nakhon Ratchasima, Thailand	sec(at)apctp.org

* HOST(Applicant)

Name	Affiliation	E-mail
-

* DATE / TIME

2010-07-05, 2:00pm

* PLACE

Seminar room 512, APCTP Headquarters, Pohang

* ABSTRACT

First principles calculations can be used to study many material properties from the fundamental ground. This talk will cover the calculations of natural vibration frequencies (local vibration modes) of impurities and defects in crystals. These vibration frequencies can be probed experimentally by infrared spectroscopy. After a brief review of the computation techniques and details, two cases will be explained. The first case covers the vibration frequencies of hydrogen atoms in GaN and ZnO where the vibration mode is very distinct from the crystal phonon modes. Therefore, reduce mass approach can be used and the calculations can be done by decoupled the vibration from the rest of the system. However, special treatment of the anharmonicity is needed in these particular cases due to the large vibration amplitude. The second case covers the calculation of the defect systems that have the vibration modes close to that of crystal phonon modes. For the second case, the full dynamic matrix calculations are needed.

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