Skandija trifluorīda struktūras pētīšana, izmantojot molekulāro dinamiku
Date
2016
Authors
Rafaļskis, Jurijs
Journal Title
Journal ISSN
Volume Title
Publisher
Latvijas Universitāte
Abstract
Skandija fluorīds (ScF3) ir interesants materiāls, kuram plašā temperatūras diapazonā no 10 līdz 1100 K piemīt negatīvā termiskā izplešanās. Šī darbā ietvaros tiek pētīta ScF3 režģa struktūra, izmantojot klasisko un ab initio molekulārās dinamikas (MD) pieeju CP2K programmas ietvaros. Darbā tika pārbaudīti dažādi MD aprēķinu parametri un aprēķinu rezultātu stabilitāte atkarībā no izvelētā ScF3 superšūnas izmēra un MD laika soļa lieluma, tika izpētīta vidējās režģa konstantes atkarība no temperatūras npT (izobāriska-izotermiska) ansamblī, iegūts leņķusadalījums Sc-F-Sc atomiem, Sc atoma radiālā sadalījuma funkcija, kā arī tika izstrādāti datu apstrādes programmatūras rīki. Rezultāti, kas iegūti ar klasiskās un ab initio MD pieejām tika salīdzināti gan savstarpēji, gan ar eksistējošiem eksperimentālajiem un teorētiskajiem literatūras datiem. Parādīts, ka ab initio molekulārā dinamikā spēj kvalitatīvi reproducēt negatīvās termiskās izplešanās efektu.
Scandium fluorine is an interesting material which exhibits negative thermal expansion property over a wide range of temperatures (from 10 K to 1100 K). In this bachelor thesis the lattice structure of ScF is studied using two different techniques: classical and ab initio molecular dynamics using the CP2K code. Depending on the different parameters used, such as supercell size and simulation time step, stability of MD simulation results is also estimated. The average lattice constant dependence on temperature for an npT ensemble, inter-atomic angle distribution for Sc-F-Sc atomic chains, as well as Sc radial distribution function calculations were performed in this work. Data analysis utilities and script were created for these purposes. We have compared the results of classical versus molecular calculations and cross-checked them with gathered theoretical and experimental data available in literature. Ab initio molecular dynamics calculations in this work have shown the ability to reproduce the effect of negative thermal expansion qualitatively using Ab initio molecular dynamics. Keywords: Negative thermal expansion, ScF, classical molecular dynamics, ab initio molecular dynamics, supercell size.
Scandium fluorine is an interesting material which exhibits negative thermal expansion property over a wide range of temperatures (from 10 K to 1100 K). In this bachelor thesis the lattice structure of ScF is studied using two different techniques: classical and ab initio molecular dynamics using the CP2K code. Depending on the different parameters used, such as supercell size and simulation time step, stability of MD simulation results is also estimated. The average lattice constant dependence on temperature for an npT ensemble, inter-atomic angle distribution for Sc-F-Sc atomic chains, as well as Sc radial distribution function calculations were performed in this work. Data analysis utilities and script were created for these purposes. We have compared the results of classical versus molecular calculations and cross-checked them with gathered theoretical and experimental data available in literature. Ab initio molecular dynamics calculations in this work have shown the ability to reproduce the effect of negative thermal expansion qualitatively using Ab initio molecular dynamics. Keywords: Negative thermal expansion, ScF, classical molecular dynamics, ab initio molecular dynamics, supercell size.
Description
Keywords
Fizika , Negatīva termiska izplešanas , ScF3 , Klasiska molekulāra dinamika , Ab initio molekulāra dinamika , Superšūnas izmērs.