Opis anomalnih lastnosti vode s preprostim dvorazsežnim modelom : podatki, ustvarjeni pri doktorskem delu

Ogrin, Peter (author)

Preprost dvo-dimenzionalni model smo uporabili za opis (anomalnih) lastnosti vode. Prednosti takega modela so predvsem večja računska učinkovitost, enostavna vizualizacija sistema ter primernost za uporabo v statistično-mehanskih teorijah. Uporabili smo vrtnični model ter Mercedes-Benz model, pri katerem so molekule modelirane kot Lennard-Jonesovi diski z eksplicitnim orientacijsko-odvisnimi potencialom za vodikove vezi. Cilj raziskave je bil preučiti lastnosti vrtničnega modela v različnih sistemih, poleg tega pa razviti pristope, ki nam omogočajo čim hitrejši izračun lastnosti (tekoče) vode. S simulacijami smo določili območja anomalnih lastnosti vrtničnega modela ter jih razvrstili v hierarhijo. Ta hierarhija je nekoliko drugačna kot pri pravi vodi in je odvisna od parametrizacije modela. Pomembna anomalna lastnost vode je tudi njeno pestro fazno obnašanje. S termodinamično perturbacijsko teorijo smo določil ravnotežno krivuljo tekočina-para ter perkolacijsko krivuljo. Nekoliko več faznih prehodov smo uspeli določiti z algoritmom gnezdenega vzorčenja. Ker pa smo hoteli fazni diagram določiti na čim bolje enostaven način, smo razvili pristop, ki z uporabo metod nenadzorovanega strojnega učenja praktično avtomatsko določi celoten fazni diagram modela vode. S simulacijami molekulske dinamike smo preučili obnašanje vrtničnega modela vode v statičnem in dinamičnem električnem polju. V močnem polju molekule vode izgubijo vse značilnosti vode in se obnašajo kot dipoli v električnem polju. Če je jakost polja približno enaka jakosti vodikovih vezi, pa postanejo anomalne lastnosti vode bolj izrazite. Razvili smo model, ki opiše frekvenčni odziv vode na nihajoče električno polje glede na statistiko vodikovih vezi. Razvili smo tudi strukturni model vode, ki temelji na analitičnem modelu vode. Model generira snežinkam podobne strukture, ki služijo kot približek strukture tekoče vode. Analitičen model smo s tem razvili v kompleten model, ki omogoča izračun termodinamičnih, dinamičnih in strukturnih lastnosti vode.

• Language: Slovenian
• Keywords: model vode, vrtnični model, Mercedes-Benz model, statistična mehanika, statistična termodinamika, fazni diagram, električno polje, analitični model
• Typology: 2.20 - Complete scientific database of research data
• Geographic coverage: Ljubljana
• Time coverage: 2021-2025
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Year: 2025
• PID: 20.500.12556/RUL-169446
• Data col. methods: Measurements and tests

Note

README datoteka je prisotna znotraj RAR arhiva / The README file is present within the RAR archive

• Publication date in RUL: 17.06.2025

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: English
• Title: Description of anomalous water properties with a simple two-dimensional model : data generated in doctoral work

Abstract

A simple two-dimensional model was used to describe the (anomalous) properties of water. The advantages of such a model are mainly the increased computational efficiency, the simple visualisation of the system and the suitability for use in statistical-mechanical theories. We used the rose model and Mercedes-Benz model, in which the molecules are modelled as Lennard-Jones discs with explicit orientation-dependent potentials for the hydrogen bonds. The aim of the research was to investigate the properties of the rose model in different systems and furthermore to develop approaches that allow us to calculate the properties of (liquid) water as fast as possible. We used simulations to determine the anomalous regions of the rose model and organise them into a hierarchy. This hierarchy differs from that of real water and depends on the parameterisation of the model. Another important anomalous property of water is its diverse phase behaviour. Using thermodynamic perturbation theory, we determined the liquid-vapor coexistence line and percolation line. More phase transitions were determined using the nested sampling algorithm. However, since we wanted to determine the phase diagram as simply as possible, we developed an approach that virtually automatically determines the complete phase diagram of the water model using unsupervised machine learning methods. Using molecular dynamics simulations, we investigated the behaviour of the rose water model in static and dynamic electric fields. In a strong field the water molecules loose all the properties of water and behave like dipoles in an electric field. However, when the field strength is approximately equal to the strength of the hydrogen bonds, the anomalous properties of water become even more pronounced. We have developed a model that describes the frequency response of water to an oscillating electric field based on the statistics of the hydrogen bonds. We have also developed a structural model of water based on an analytical model of water. The model generates snowflake-like structures that serve as an approximation of the structure of liquid water. The analytical model has thus been developed into a complete model that enables the calculation of the thermodynamic, dynamic and structural properties of water.

• Keywords: water model, rose model, Mercedes-Benz model, statistical mechanics, statistical thermodynamics, phase diagram, electric field, analytical model

Projects

• Funder: ARIS - Slovenian Research and Innovation Agency
• Project number: P1-0201
• Name: Fizikalna kemija