Stohastičko pretraživanje konfiguracijskih izomera Au4, Au6 i Au8

master's thesis

• Title (english): Stochastic search of Au4, Au6 and Au8 configurational isomers
• Author: Antonio Ljulj
• Mentor: Valerije Vrček (mentor)
• Committee member: Valerije Vrček (predsjednik povjerenstva)
• Committee member: Davor Šakić (član povjerenstva)
• Committee member: Tin Weitner (član povjerenstva)
• Granter: University of Zagreb; Faculty of Pharmacy and Biochemistry; (Department of organic chemistry); Zagreb
• Defense date and country: 2024-09-10, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Chemistry; Organic Chemistry

Abstract

U ovom radu provedeno je stohastičko pretraživanje struktura malih klastera zlata Aun (n = 2 – 8), s ciljem identifikacije i karakterizacije osnovnih strukturnih jedinica koje su prikladne za opis formiranja nanočestica zlata. Odabrani klasteri predstavljaju osnovne građevne blokove na kojima se temelje složenije strukture. Korištena procedura „Kick" pokazala se kao vrlo učinkovit i pouzdan alat, posebno u pogledu brzine i preciznosti u pretraživanju plohe potencijalne energije tetramera, heksamera i oktamera zlata. Osim toga, važnu ulogu ima i primijenjena teorijska razina DFT u kvantno-kemijskim izračunima, o kojoj ovise rezultati prirode struktura (minimumi ili stacionarne točke).
Kako se broj atoma zlata u oligomerima povećavao, zabilježen je rast broja mogućih konfiguracijskih i konformacijskih izomera, čime se znatno povećava složenost sustava. Za čestice Au4 locirana su 3 stabilna izomera, za Au6 je locirano 9 struktura te je za Au8 locirano 19 struktura koje su pravi minimumi. Istovremeno, s povećanjem broja atoma zlata u klasterima, zabilježeno je i povećanje raspona relativnih energetskih razlika između različitih klastera (za Au4 raspon oko 42 kJ/mol, za Au6 170 kJ/mol te za Au8 oko 140 kJ/mol), što dodatno otežava identifikaciju najstabilnijih struktura.
Prikazana metoda stohastičkog pretraživanja, u kombinaciji s DFT izračunima, pokazala se izuzetno korisnom ne samo za razumijevanje strukturne raznolikosti malih zlatnih klastera, već i za
širu primjenu u proučavanju većih molekulskih sustava. Ova metodologija može se učinkovito koristiti i za proučavanje interakcija između lociranih izomera i biološki važnih spojeva, otvarajući mogućnosti za daljnja istraživanja na granici nanotehnologije i biokemije.

Abstract (english)

In this work, a stochastic search of the structures of small Aun gold clusters (n = 2 – 8) was carried out, with the aim of identifying and characterizing the basic structural units that are suitable for describing the formation of gold nanoparticles. The selected clusters represent the basic building blocks on which more complex structures are based. The used "Kick" procedure proved to be a very effective and reliable tool, especially in terms of speed and precision in the search of the surface potential energy of tetramers, hexamers and octamers of gold. In addition, the applied theoretical level of DFT plays an important role in quantum chemical calculations, on which the results of the nature of the structures (minima or stationary points) depend.
As the number of gold atoms in the oligomers increased, an increase in the number of possible configurational and conformational isomers was recorded, which significantly increases the complexity of the system. 3 stable isomers were located for Au4 particles, 9 structures were located for Au6, and 19 structures were located for Au8, which were true minima. At the same time, with the increase in the number of gold atoms in the clusters, an increase in the range of relative energy differences between different clusters was recorded (for Au4 the range is about 42 kJ/mol, for Au6 170 kJ/mol and for Au8 about 140 kJ/mol), which further complicates identification of the most stable structures.
The presented stochastic search method, in combination with DFT calculations, proved to be extremely useful not only for understanding the structural diversity of small gold clusters, but also for wider application in the study of larger molecular systems. This methodology can also be effectively used to study interactions between localized isomers and biologically important compounds, opening possibilities for further research at the border of nanotechnology and biochemistry.

• Keywords: nanočestice; stohastičko pretraživanje; teorija funkcionala gustoće; DFT
• Keywords (english): nanoparticles; stochastic search; density functional theory; DFT
• Language: croatian
• URN:NBN: urn:nbn:hr:163:360783
• Study programme: Title: Pharmacy - integrated undergraduate and graduate - university study; Study programme type: university; Study level: integrated undergraduate and graduate; Academic / professional title: sveučilišni magistar farmacije (sveučilišni magistar farmacije)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2024-10-11 09:57:31