15336

13762

كارشناسي ارشد

حالت جامد

اصفهان : دانشگاه صنعتي اصفهان

1398

هجده، 153ص. : مصور (رنگي)، جدول، نمودار

جواد هاشمي‌فر

اسماعيل عبدالحسيني سارسري

مجتبي اعلايي، فرهاد فضيله

1398/09/11

كتابنامه

فيزيك

فيزيك

1398/09/13

2581507

First principles investigation of the effects of pressure on topological properties of AlB 2 semimetal Saeid Abedi September 22 2019 Department of Physics Isfahan University of Technology Isfahan 84156 83111 IranDegree Master of Science Language FarsiSupervisor Seyed Javad Hashemifar Assoc Prof hashemifar@cc iut ac ir AbstractThe study of electronic structure topology of crystalline materials has been one of the major fields in condensedmatter physics during the last decade The main motivation for this research came from the discovery of topo logical insulators although the focus has recently been shifted towards topological semimetals and even metals Topological materials are a new class of quantum matters whose special electronic structure in the momentumspace leads to the formation of a topological invariance Theoretical predictions particularly first principleselectronic structure calculations based on the density functional theory DFT have played an important rolein the exploration of almost all topological electronic materials Up to now different topological phases havebeen investigated and new materials have been discovered in the field In a recent study using experimentaltechniques Aluminum Diboride AlB 2 has been introduced as a topological semimetal In the current work electronic and topological features of AlB 2 semimetal were investigated in both equilibrium structure and alsounder high pressure Some other compounds with similar structures were studied in this thesis as well Forthis purpose the first step was to calculate the electronic characteristics of AlB 2 using DFT calculations andthen extracting its Wannier functions in order to construct a tight binding hamiltonian This hamiltonian wasthen used to compute the topological invariant and surface states which are the manifestations of non trivialtopology in bulk materials To study the effects of pressure on topological properties of AlB 2 first using theevolutionary algorithm the stable structure of this material was searched in different pressures and then thesenew structures were investigated more thoroughly by calculating their electronic features Afterward Wannierfunctions were calculated for each structure and as a result the calculation of the Berry phase for all the newstructures became possible In the end using the calculated electronic structures and Berry phases differenttopological stable phases were analyzed In addition the results on the calculation of electronic features andtopological invariants of some similar materials were also offered Keywordstopological semimetal topological invariant surface states band structure density functional theory DFT calculations Wannier functions Berry phase

جواد هاشمي‌فر

اسماعيل عبدالحسيني سارسري

مجتبي اعلايي، فرهاد فضيله