Ab initio analýza struktury a stability fází Ti2Sn a Co1,5Sn

Bc. Petr Čípek

Bachelor's thesis

Ab initio analysis of structure and stability of Ti2Sn and Co1.5Sn phases

Abstract:

Tato práce se zabývá ab initio analýzou vlastností struktur Ti2Sn a Co1,5Sn, v rámci které byly dále zkoumány příbuzné struktury Co2Sn, Double_1 Co3Sn2, Double_2 Co3Sn2 a čistý hcp kobalt. Rovnovážné mřížkové parametry studovaných struktur jsou následující: hcp Co a = b = 2,491 Å a c = 4,025 Å, Ti2Sn a = b = 4,743 Å a c = 5,626 Å, Co2Sn a = b = 4,289 Å a c = 5,204 Å, Co1,5Sn a = b = 4,220 Å a c = 5,066 Å, Double_1 Co3Sn2 a = 4,184 Å b = 4,101 Å a c = 5,173 Å a Double_2 Co3Sn2 a = 4,183 Å b = 4,174 Å a c = 5,235 Å. Nezdvojené struktury si oproti strukturám zdvojeným při relaxaci zachovaly ideální mřížkové úhly hexagonální struktury. Průměrné magnetické momenty na atom jsou ̅μ(hcp Co) = 1,5976 μB atom−1, ̅μ(Co2Sn) = 0,4174 μB atom−1, ̅μ(Co1,5Sn) = 0,4866 μB atom−1, ̅μ(Double_1 Co3Sn2) = 0,4522 μB atom−1 a ̅μ(Double_2 Co3Sn2) = 0,4998 μB atom−1. Tvorné entalpie analyzovaných struktur vztažené k čistým prvkům ve standardním stavu jsou ∆H(Ti2Sn) = −31,5996 kJ (mol at.)−1, ∆H(Co2Sn) = 14,4193 kJ (mol at.)−1, ∆H(Co1,5Sn) = 4,8089 kJ (mol at.)−1, ∆H(Double_1 Co3Sn2) = 8,0163 kJ (mol at.)−1 a ∆H(Double_2 Co3Sn2) = 10,017 kJ (mol at.)−1. Tvorné teplo vakance ve struktuře Co1,5Sn je ∆H(Va Co1,5Sn) = 0,5685 eV Va.−1, ve zdvojené struktuře Double_1 je ∆H(Va Double_1 Co3Sn2) = 0,7350 eV Va.−1 a v Double_2 dosahuje hodnoty ∆H(Va Double_2 Co3Sn2) = 0,8387 eV Va.−1.

Abstract:

This thesis deals with ab initio analysis of properties of Ti2Sn and Co1,5Sn structures. Related structures Co2Sn, Double_1 Co3Sn2, Double_2 Co3Sn2 and pure hcp Co were also analysed. Equilibrium lattice parameters of the structures mentioned above are as follows: hcp Co a = b = 2.491 Å and c = 4.025 Å, Ti2Sn a = b = 4.743 Å and c = 5.626 Å, Co2Sn a = b = 4.289 Å and c = 5.204 Å, Co1,5Sn a = b = 4.220 Å and c = 5.066 Å, Double_1 Co3Sn2 a = 4.184 Å, b = 4,101 Å and c = 5.173 Å and Double_2 Co3Sn2 a = 4.183 Å, b = 4.174 Å and c = 5.235 Å. The lattice angles of Double structures were deformed compared to the ideal hexagonal ones found in the remaining structures. The average magnetic moments per atom are ̅μ(hcp Co) = 1.5976 μB atom−1, ̅μ(Co2Sn) = 0.4174 μB atom−1, ̅μ(Co1.5Sn) = 0.4866 μB atom−1, ̅μ(Double_1 Co3Sn2) = 0.4522 μB atom−1 and ̅μ(Double_2 Co3Sn2) = 0.4998 μB atom−1. The heats of formation of analysed structures related to the pure elements in the standard state are ∆H(Ti2Sn) = −31.5996 kJ (mol at.)−1, ∆H(Co2Sn) = 14.4193 kJ (mol at.)−1, ∆H(Co1.5Sn) = 4.8089 kJ (mol at.)−1, ∆H(Double_1 Co3Sn2) = 8.0163 kJ (mol at.)−1 and ∆H(Double_2 Co3Sn2) = 10.017 kJ (mol at.)−1. The heat of formation of vacancy in structure Co1.5Sn is ∆H(Va Co1.5Sn) = 0.5685 eV Va.−1. In Double structures, it reached values ∆H(Va Double_1 Co3Sn2) = 0.7350 eV Va.−1 and ∆H(Va Double_2 Co3Sn2) = 0.8387 eV Va.−1.

Keywords

ab initio výpočty, teorie funkcionálu hustoty, program VASP, kobalt, Ti2Sn, Co1, 5Sn, tvorné teplo, ab initio calculations, density functional theory, VASP code, cobalt, heat of formation

Language used: Czech

Date on which the thesis was submitted / produced: 1. 6. 2022

Thesis defence

• Date of defence: 27. 6. 2022
• Supervisor: doc. Mgr. Jana Pavlů, Ph.D.
• Reader: Ing. Monika Všianská, Ph.D.

Masaryk University

Faculty of Science

Bachelor programme / field:
Chemistry / Chemistry