Numerična simulacija razprševanja odboja enoatomnih plinov na kristalni rešetki kovine

Radosavljević, Uroš (author), Šajn, Viktor (mentor)

Pri makroskopski analizi toka fluida se običajno upoštevata poenostavitvi o zvezno porazdeljeni snovi – kontinuumu in o nični relativni hitrosti delca fluida ob steni. Oba ne upoštevata molekularno naravo fluida kot snovi ker je upor toka odvisen od asimetričnosti kota odboja molekul od stene. V idealnem primeru je kot po trku molekule fluida s steno enak kotu pred trkom, saj se takrat na steno ne prenaša tangencialna sila, posledično pa je viskoznost kot makroskopska veličina nična. Izdelana je bila dvo- in tridimenzionalna numerična simulacija razprševanja odboja enoatomnih plinov (argon in kripton) na monokristalnih rešetkah čistih kovin (srebro in platina). Za analizo je bil uporabljen programski paket LAMMPS. Vsi izračuni so potekali pri energijah, kjer kvantni vplivi niso imeli značilnega vpliva. Določena je bila porazdelitev gostote verjetnosti odbojev izhodnih kotov glede na karakteristične vpadne kote 30, 45 in 60 stopinj glede na normalo pri različnih orientacijah kristalnih rešetk (100 in 111) za primer dvo- in tridimenzionalnega toka. Podane so bile primerjave z opravljenimi raziskavami na tem področju. Razširili smo rezultate iz dvodimenzionalnih modelov na tridimenzionalno skalo ter predstavili dobljene rezultate.

• Language: Slovenian
• Keywords: molekularna dinamika, sipanje delcev, trki, numerična simulacija, monokristali, programski paket LAMMPS
• Work type: Master's thesis/paper
• Typology: 2.09 - Master's Thesis
• Organization: FS - Faculty of Mechanical Engineering
• Place of publishing: Ljubljana
• Publisher: [U. Radosavljević]
• Year: 2019
• Number of pages: XXVII, 95 str.
• PID: 20.500.12556/RUL-112648
• UDC: 544.272:004.942(043.2)
• COBISS.SI-ID: 16962843
• Publication date in RUL: 30.10.2019

RADOSAVLJEVIĆ, Uroš, 2019, Numerična simulacija razprševanja odboja enoatomnih plinov na kristalni rešetki kovine [online]. Master’s thesis. Ljubljana : U. Radosavljević. [Accessed 27 June 2025]. Retrieved from: https://repozitorij.uni-lj.si/IzpisGradiva.php?lang=eng&id=112648

Secondary language

• Language: English
• Title: Numerical simulation of outbound angle scattering of monatomic gasses on a metal crystal lattice

Abstract

When an analysis of a fluid flow is performed on a macroscopic level, often two assumptions are taking place. First is an assumption of a continuously distributed matter (continuum), the second is a zero relative fluid velocity at the fluid-surface interface, often referred as no-slip condition. Both assumptions do not count in the atomic nature of a real fluid, since the flow friction is dependant on the asymmetricity of the outbound angle when an atom collision is taking place. In the ideal case, after a flow atom collided with the wall surface the inbound angle is the same as the outbound angle, because only then, no tangential force has been transferred to the wall, consequently the fluid viscosity, as a macroscopic quantity, is zero. A two- and three-dimensional numerical simulation of the outbound angle scattering of monatomic gases (argon and krypton) on monocrystal lattices of pure metals (silver and platinum) was made. For the analysis we used a software called LAMMPS. All the calculations took place with energies where quantum nature of the materials was not significant. An outbound angle probability density distribution was made for inbound angles of 30, 45 and 60 degrees regarding the surface normal at different lattice orientations (100 and 111). We had compared our two-dimensional scattering results with the measurements in the literature, broadened them to three-dimensional scale and presented the results.

• Keywords: molecular dynamics, particle scattering, collisions, numerical simulation, monocrystals, LAMMPS program, no-slip condition