** Notic
e and Invitation**Oral Defense of Doctoral Dissertation

\n

\nDoctor of Philosophy in Computational Science and Informatics

\nDepartment of Computational and Data Sciences

\nCollege of Science

\nGeorge Mason University

**Swabir Silayi**

\nBachelor of Science\, Fatih University\, 20
09

\nMaster of Science\, Fatih University\, 2011

\nMaster of Sci
ence\, Old Dominion University\, 2013

< strong>ELECTRONIC STRUCTURE AND DYNAMICS ANALYSIS OF NOBLE METALS BY A TIG HT-BINDING PARAMETRIZATION

\nWe
dnesday\, December 04\, 2019\, 3:00 p.m.

\nExploratory Hall\, Room 33
01

All are invited to attend.

\n**Committee**

\nDr. Estela Blaisten – Committee Chair

\nDr. Dimitrios A. Papaconstantopoulos

\nDr. James Glasbrenner

\nDr. Eduardo Lopez

Theoretical studies of the properties of mat erials are important as they serve to narrow the focus of what are normall y time consuming and costly experimental searches. In modeling these mater ials\, first-principles density functional methods have been proven to qui te effective. They have the drawback of being computationally expensive an d\, to mitigate this\, faster approaches have been developed such as the t ight-binding model.

\nWe have used the Naval Research Lab (NRL) tigh t-binding (TB) method to study the electronic and mechanical properties of the noble metals. The tight-binding Hamiltonians are determined from a fi t that has a non-orthogonal basis and reproduces the electronic structure and total energy values of first-principles linearized augmented plane wav e calculations. In order to perform molecular dynamics simulations\, we de veloped new TB parameters that work well at smaller interatomic distances. We analyze fcc\, bcc and sc periodic structures and we demonstrate that t he TB parameters are transferable and robust for calculating additional dy namical properties which they had not been fitted to.

\nTo do this\, we calculated phonon frequencies and density of states at finite temperat ure and performed simulations to determine the coefficients of thermal exp ansion and the atomic mean squared displacement. The energies for vacancy formation were also calculated as were the binding energies for fcc-based\ , bcc-based and icosahedral clusters of different sizes. The results compa red very well with experimental observations and independent first-princip les density functional calculations.

\nExtending from the single ele ment systems\, we develop parameter sets for the Cu-Ag and Ag-Au noble met al binary alloys as well. These parameters were fit to the structures 2\, 10\, 12 − 3\,3\, with the and representing the different combinations of \ , and in addition to the fcc \, and .

\nAs an output of this exte nsion to the binary systems\, the following quantities were reproduced in good agreement with available experimental and theoretical values: elastic constants\, densities of electronic states as well as the total energies of additional crystal structures that were not included in the original fi rst-principles database. We also used this TB parametrization for the allo y systems to successfully perform molecular dynamics simulations and deter mined the energies for vacancy formation\, temperature dependence of the c oefficient of thermal expansion\, the mean squared displacement and phonon spectra. In addition we show that these TB parameters work for determinin g binding energies and bond lengths of Cu-Ag fcc-like clusters.

\n DTSTART;TZID=America/New_York:20191204T150000 LOCATION:Exploratory Hall\, Room 3301\, Fairfax Campus SEQUENCE:0 SUMMARY:Oral Defense of Doctoral Dissertation – Computational Science and I nformatics – ELECTRONIC STRUCTURE AND DYNAMICS ANALYSIS OF NOBLE METALS BY A TIGHT-BINDING PARAMETRIZATION – SWABIR SILAYI URL:https://cos.gmu.edu/cds/event/oral-defense-of-doctoral-dissertation-com putational-science-and-informatics-electronic-structure-and-dynamics-analy sis-of-noble-metals-by-a-tight-binding-parametrization-swabir-silayi/ X-COST-TYPE:free X-INSTANT-EVENT:1 END:VEVENT END:VCALENDAR