University of Oulu

Applications of density functional theory for modeling metal-semiconductor contacts, reaction pathways, and calculating oxidation states

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Author: Posysaev, Sergei1,2
Organizations: 1University of Oulu Graduate School
2University of Oulu, Faculty of Science, Physics
Format: ebook
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 1.2 MB)
Persistent link: http://urn.fi/urn:isbn:9789526221328
Language: English
Published: Oulu : University of Oulu, 2018
Publish Date: 2018-11-30
Thesis type: Doctoral Dissertation
Defence Note: Academic Dissertation to be presented with the assent of the Faculty of Science, University of Oulu, for public discussion in the Auditorium IT 116, on December 14th, 2018 at 12 o’clock noon.
Tutor: Professor Matti Alatalo
Reviewer: Professor Bernardo Barbiellini
Professor Kalevi Kokko
Opponent: Professor Marcel Sluiter
Kustos: Professor Matti Alatalo
Description:

Abstract

Density functional theory (DFT) is a well-established tool for calculating the properties of materials. The volume of DFT-related publications doubles every 5‚Äď6 years, which has resulted in the appearance of continuously growing open material databases, containing information on millions of compounds. Furthermore, the results of DFT computations are frequently coupled with experimental ones to strengthen the computational findings.

In this thesis, several applications of DFT related to physics and chemistry are discussed. The conductivity between MoS‚āā and transition metal nanoparticles is evaluated by calculating the electronic structure of two different models for the nanoparticles. Chemical bonding of Ni to the MoS‚āā host is proven by the system‚Äôs band alignment. To meet the demand for cleaner fuel, the applicability of the (103) edge surface of molybdenum disulfide in relation to the early stages of the hydrodesulfurization (HDS) reaction is considered. The occurrence of the (103) edge surface of molybdenum disulfide in the XRD patterns is explained. A method for calculating oxidation states based on partial charges using open materials databases is suggested. We estimate the applicability of the method in the case of mixed valence compounds and surfaces, showing that DFT calculations can be used for the estimation of oxidation states.

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Tiivistelmä

Tiheysfunktionaaliteoria (density functional theory, DFT) on yleisesti k√§ytetty ty√∂kalu laskennallisessa materiaalitutkimuksessa. DFT:ll√§ tuotettujen julkaisujen m√§√§r√§ kaksinkertaistuu 5‚Äď6 vuoden v√§lein, mink√§ johdosta k√§ytett√§viss√§ on jatkuvasti kasvava m√§√§r√§ avoimia materiaalitietokantoja, joihin on talletettu miljoonien yhdisteiden ominaisuuksia. DFT-laskujen tuloksia t√§ydennet√§√§n my√∂s usein kokeellisilla tuloksilla.

T√§ss√§ ty√∂ss√§ tarkastellaan tiheysfunktionaaliteorian sovelluksia fysiikassa ja kemiassa. MoS‚āā:n ja metallisten nanopartikkelien v√§list√§ johtavuutta on tutkittu mallintamalla erilaisia nanopartikkeleita. Nikkelin ja MoS‚āā:n v√§linen kemiallinen sidos selittyy systeemin energiav√∂iden kohdistumisella. MoS‚āā:n (103)-pinnan soveltuvuutta rikinpoistoreaktion varhaisissa vaiheissa on tutkittu tarkoituksena l√∂yt√§√§ uusia menetelmi√§ puhtaan polttoaineen tuottamiseksi. My√∂s (103)-pinnan esiintyminen r√∂ntgendiffraktiokuvissa selitet√§√§n. Ty√∂ss√§ on my√∂s esitetty menetelm√§ hapetustilojen laskemiseksi tietokannoista l√∂ytyvien laskettujen varausjakaumien avulla. Menetelm√§n soveltuvuutta on tarkasteltu erilaisille yhdisteille ja pinnoille. T√§m√§ tarkastelu osoittaa, ett√§ DFT-tuloksia voidaan k√§ytt√§√§ hapetustilojen laskemiseen.

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Series: Report series in physical sciences
ISSN: 1239-4327
ISSN-L: 1239-4327
ISBN: 978-952-62-2132-8
ISBN Print: 978-952-62-2131-1
Issue: 123
Subjects:
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