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Prostorske korelacije in dinamika v tekočinah z vodikovimi vezmi
ID Cerar, Jure (Avtor), ID Tomšič, Matija (Mentor) Več o mentorju... Povezava se odpre v novem oknu

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Izvleček
S kombinacijo eksperimentalnih in teoretičnih raziskovalnih pristopov v povezavi z metodo sipanja rentgenske svetlobe in računalniškimi simulacijami smo preučevali strukturo in dinamiko različnih sistemov, v katerih je povezovanje molekul z vodikovimi vezmi pomemben dejavnik pri njihovem strukturiranju. Raziskave so zaobsegale tako strukturo v smislu molekulskih konformacij, preferenčnega orientiranja in prostorske organizacije molekul kot tudi njihovega povezovanja v skupke na supramolekularnem nivoju. Iz rezultatov simulacij smo po teoretični metodi dopolnjenega sistema izračunali rentgensko sipanje modelnih sistemov in ga primerjali z eksperimentalnimi rezultati. Simulacije so nam na ta način priskrbele neposreden vpogled v strukturo in dinamiko modelnih sistemov, laboratorijski eksperimenti so nam pa služili kot kriterij za oceno pravilnosti uporabljenega modela. Dinamiko sistemov smo raziskali preko trendov spreminjanja lastnih difuzijskih koeficientov molekul in življenjskega časa različnih tipov vodikove vezi, reološke lastnosti smo pa določili s pomočjo rezultatov neravnotežnih simulacij molekulske dinamike in literaturnih eksperimentalnih podatkov. Primerjava vseh teh rezultatov nam je omogočila vpogled v funkcionalne povezave med strukturnimi in dinamičnimi lastnostmi preučevanih sistemov. Osnovna ideja raziskav je bila postopna aplikacija metodologije osnovane na metodi dopolnjenega sistema na vse kompleksnejše sisteme z velikimi strukturnimi segmenti in makromolekulami. To je zahtevalo bistveno pohitritev izračunov po metodi dopolnjenega sistema – s korenito modifikacijo osnovne programske kode in njeno paralelizacijo na več nivojih smo dosegli nekaj velikostnih redov hitrejše izračune. Raziskave smo pričeli z relativno preprostim čistim tekočim n-butanolom, nadaljevali z zahtevnejšim 1,4-butandiolom in nato še s homologno vrsto terminalnih diolov od etilen glikola do 1,5-pentandiola. Sledila je raziskava precej kompleksnejše binarne vodne mešanice hidrotropnega tert-butanola v celotnem koncentracijskem območju z zelo raznolikim strukturnim in dinamičnim obnašanjem ter strukturnimi segmenti reda velikosti nekaj nanometrov in na koncu še raziskava makromolekulskih raztopin neionskega surfaktanta Brij 35 v organskih in organsko-vodnih medijih. Rezultati dokazujejo, da uporabljena metodologija omogoča celostno interpretacijo razmerij in povezav med strukturo, dinamiko in reološkimi lastnostmi tekočin na intra-, inter- in supramolekularnem nivoju podrobnosti tudi za kompleksnejše sisteme z velikimi strukturnimi segmenti in makromolekulami, in izpostavljajo prednosti te metodologije pred klasičnimi izključno eksperimentalnimi ali izključno teoretičnimi pristopi.

Jezik:Slovenski jezik
Ključne besede:rentgensko sipanje, molekulska dinamika, vodikova vez, struktura tekočin, transportne lastnosti tekočin
Vrsta gradiva:Doktorsko delo/naloga (mb31)
Tipologija:2.08 - Doktorska disertacija
Organizacija:FKKT - Fakulteta za kemijo in kemijsko tehnologijo
Leto izida:2021
COBISS.SI-ID:85243139 Povezava se odpre v novem oknu
Datum objave v RUL:29.09.2021
Število ogledov:194
Število prenosov:41
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Sekundarni jezik

Jezik:Angleški jezik
Naslov:Spatial correlations and dynamics in hydrogen-bonded liquids
Izvleček:
We studied the structure and dynamics of several very different chemical systems in which the association of molecules with hydrogen bonds plays an important role in their properties. We used a combination of experimental and theoretical research approaches in conjunction with the X-ray scattering method and molecular dynamics simulations. The structure was studied in terms of molecular conformations, preferred orientation and spatial organization of molecules, and their association to clusters at the supramolecular level. Using the theoretical complemented system approach, the results of the molecular dynamics simulations were used to calculate the scattering intensities of the modelled systems, which were then compared with the experimental X-ray scattering data. In this way, the simulations provided us with a direct insight into the structure and dynamics of the model systems, as the laboratory experiment served as a criterion for assessing the correctness of the model used. The system's dynamics was studied in terms of the molecular self-diffusion coefficients and the lifetime of the different types of hydrogen bonds in the system. Similarly, the rheological properties or viscosity trends were investigated using the results of the nonequilibrium molecular dynamics simulations and the experimental literature data. A comparison of all these results gave us an insight into the functional relationship between the structural and dynamic properties of the system under study. The basic idea of our research was to gradually apply the methodology based on the complemented system approach method to increasingly complex chemical systems with large structural segments and even macromolecules. This required a significant acceleration of the calculations using the complemented system approach. Through significant modification of the basic program code and its parallelization at several levels, we achieved an acceleration of the calculations by several orders of magnitude. Our studies of various chemical systems began with a study of a relatively simple pure liquid n-butanol, continued with two studies of the more complex 1,4-butanediol, and a study of a homologous series of terminal diols from ethylene glycol to 1,5-pentanediol. This was followed by a study of a rather complex binary aqueous mixture of hydrotropic tert-butanol over the entire concentration range with very versatile structural and dynamic behaviour and structural segments on the order of a few nanometres. Finally, a study of macromolecular systems with the non-ionic surfactant Brij 35 in organic and aqueous-organic media was also successfully completed. The results demonstrate that the methodology used provides a comprehensive insight into the relationships between the structure and the rheological-dynamic properties of fluid systems at intra-, inter- and supramolecular levels of detail, even for quite complex chemical systems with large structural segments and even macromolecules.

Ključne besede:X-ray scattering, molecular dynamics, hydrogen bond, structure of liquids, transport properties of liquids

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