Monte Carlo simulacije Mercedes-Benz modela vode

Ogrin, Peter (author), Urbič, Tomaž (mentor)

Izvedene so bile Monte Carlo simulacije v NVT ansamblu, z namenom da bi preučili strukturne in termodinamične lastnosti 2D Mercedes-Benz modela vode. Preučili smo kakšne strukturne lastnosti ima model pri različnih temperaturah in gostotah. Uporabljen model nam omogoča tudi neodvisno spreminjanje rotacijske in translacijske temperature. Zanimalo nas je kako rotacijska in translacijska temperatura ločeno vplivata na strukturne in termodinamične lastnosti sistema MB delcev pri konstantnem tlaku. Da bi pridobili informacije o lastnostih sistema pri konstantnem tlaku, so bili rezultati NVT simulacij interpolirani na konstanten tlak 0,12. Večanje gostote sistema pri konstantni temperaturi (rotacijski in translacijski) oslabi vpliv vodikovih vezi med delci, s tem postaja struktura sistema vse manj urejena. Pri konstantni gostoti pa z naraščajočo temperaturo (v tem primeru sta rotacijska in translacijska temperatura enaki) slabi vpliv vseh interakcij med delci, pri čemer ima temperatura večji vpliv na vodikove vezi, kot na van der Waalsove interakcije. V primeru konstantnega tlaka zviševanje rotacijske temperature povzroči, zmanjšanje količine vodikovih vezi v sistemu, na van der Waalsove interakcije pa nima vpliva. Nasprotno dvig translacijske temperature zmanjša tako vpliv vodikovih vezi kot tudi van der Waalsovih interakcij, a je učinek na vodikove vezi izrazitejši. Preučili smo tudi odvisnost povprečne presežne energije na delec, gostote, presežne toplotne kapacitete in presežnega kemijskega potenciala od rotacijske in translacijske temperature pri konstantnem tlaku. Pri nizkih rotacijski in translacijski temperaturi imajo nekatere termodinamične količine lokalni ekstrem. Visoka rotacijska temperatura zmanjša izrazitost anomalnih lastnosti termodinamičnih količin, ki so posledica vodikovih vezi, ter naredi sistem bolj podoben normalni tekočini.

• Language: Slovenian
• Keywords: Monte Carlo, Mercedes-Benz model vode, termodinamika, vodikove vezi
• Work type: Bachelor thesis/paper
• Typology: 2.11 - Undergraduate Thesis
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Year: 2019
• PID: 20.500.12556/RUL-109552
• COBISS.SI-ID: 1538325955
• Publication date in RUL: 05.09.2019

OGRIN, Peter, 2019, Monte Carlo simulacije Mercedes-Benz modela vode [online]. Bachelor’s thesis. [Accessed 11 April 2025]. Retrieved from: https://repozitorij.uni-lj.si/IzpisGradiva.php?lang=eng&id=109552

Secondary language

• Language: English

Abstract

Monte Carlo simulations have been performed in NVT ensemble, in order to study structural and thermodynamic properties of 2D Mercedes-Benz water model. We studied properties of the model at different temperatures and densities. The model that has been used, allows independent varying of rotational and translational temperature. We were interested in effect of separated rotational and translational temperature on both structural and thermodynamic properties of system of MB particles at constant pressure. To obtain information on properties of the system at constant pressure, results from NVT simulations have been interpolated on constant pressure 0,12. Increase in density of system at constant temperature (rotational and translational) reduces effect of hydrogen bonds between particles, as result structure of the system becomes less ordered. At constant density the effect of all interactions between particles weakens with increasing temperature (in this case rotational and translational temperature are equal), while the effect of temperature on hydrogen bonds is greater than effect on van der Waals interactions. In case of constant pressure, increase in rotational temperature causes decrease in quantity of hydrogen bonds in the system, but it doesn’t affect van der Waals interaction. However increase in translational temperature diminishes effect of hydrogen bonda on the system as well as van der Waals interactions, yet the effect on hydrogen bonds is greater. It was also investigated how average excess energy of particle, density, excess heat capacity and excess chemical potential changes with changes in translational and rotational temperature at constant pressure. At low rotational and translational temperature some of thermodynamic quantities possess local extrema. High rotational temperature diminishes distinctness of anomalous properties of thermodynamic quantities, which are consequence of hydrogen bonds, as result the system becomes more normal liquid like.

• Keywords: Monte Carlo, Mercedes-Benz water model, thermodynamics, hydrogen bonds