Struktura i svojstva dvodimenzionalnih Dion-Jacobson perovskita

master's thesis

• Title (english): Structure and properties of two-dimensional Dion-Jacobson perovskites
• Author: Bruno Mladineo
• Mentor: Ivor Lončarić (mentor)
• Mentor: Ivan Kupčić (komentor)
• Committee member: Ivan Kupčić (predsjednik povjerenstva)
• Committee member: Ivor Lončarić (član povjerenstva)
• Committee member: Damir Pajić (član povjerenstva)
• Committee member: Željko Skoko (član povjerenstva)
• Committee member: Goranka Bilalbegović (član povjerenstva)
• Granter: University of Zagreb; Faculty of Science; (Department of Physics); Zagreb
• Defense date and country: 2021-07-12, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Physics

Abstract

Dion-Jacobson perovskiti se trenutno istražuju za primjenu u svjetlosnim diodama, no zbog poteškoća pri eksperimentalnom određivanju strukture tankih slojeva saznanja o vezi strukture i karakteristika materijala se teško dobivaju. Praktično rješenje tog problema je u računalnim simulacijama struktura. Teorija funkcionala gustoće (DFT), iako najraširenija metoda za računanje svojstava materijala, nije pravi alat za nalaženje globalnog minimuma strukture. DFT računi velikih sustava računalno su zahtjevni, a traženje globalnog minimuma takve strukture koristeći DFT je i nekoliko redova veličine računalno skuplje. Rješenje problema nalazimo u kombiniranju klasičnih potencijala i algoritma skakutanja minimumima. U sklopu diplomskog rada napravljen je proces nalaženja globalnog minimuma strukture nekih Dion-Jacobson perovskita. Taj proces uključuje stvaranje aproksimativnih struktura, izračun parametara klasičnih potencijala i sam algoritam skakutanja minimumima. Istražen je utjecaj parametara algoritma na pouzdanost i brzinu nalaženja globalnog minimuma strukture. Konstruirani su perovskiti s tri različite molekule: 3AMP, 4AMP i HDA, te je na njima istražen utjecaj početnih pretpostavki na pronađene globalne minimume. Pronađene strukture su naposljetku uspoređene s DFT rezultatima i dostupnim eksperimentalnim strukturama.

Abstract (english)

Dion-Jacobson perovskites are being actively researched for application in LEDs, but the difficulties with experimentally determining the structure of thin films are making insights gained from the relation of the structure to the characteristics of the material hard to come by. The practical solution is found by running computer simulations of material structures. Density functional theory (DFT), although the most widely used method for computation of material properties is not the right tool for finding the global minima of structures. Not only are DFT calculations of large systems computationally expensive, but finding the global minima of such systems using DFT are a couple of orders of magnitude more expensive. The solution to this problem is found in combining a classical potential and the minima hopping algorithm. For this master’s thesis a process for finding global minima of some Dion-Jacobson perovskite structures was made. This process includes the creation of approximate structures, calculations of the classical potential parameters and the minima hopping algorithm itself. The effect of minima hopping parameters on the algorithms reliability and speed in finding the global minima is analysed. Perovskite structures with three different molecules were constructed: 3AMP, 4AMP and HDA, on them we analyse the effect of initial assumptions in finding the global minima. Finally, the found structures are compared to DFT results and to experimentally available structures.

• Keywords: Dion-Jacobson perovskiti; predviđanje kristalne strukture; teorija funkcionala gustoće; algoritam skakutanja minimumima
• Keywords (english): Dion-Jacobson perovskites; crystal structure prediction; density functional theory; minima hopping algorithm
• Language: croatian
• URN:NBN: urn:nbn:hr:217:713318
• Study programme: Title: Physics; specializations in: Research; Course: Research; Study programme type: university; Study level: integrated undergraduate and graduate; Academic / professional title: magistar/magistra fizike (magistar/magistra fizike)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2021-07-23 11:17:43