scholarly journals Optical Diagnostics of Supercritical CO2 and CO2-Ethanol Mixture in the Widom Delta

Molecules ◽  
2020 ◽  
Vol 25 (22) ◽  
pp. 5424
Author(s):  
Evgenii Mareev ◽  
Timur Semenov ◽  
Alexander Lazarev ◽  
Nikita Minaev ◽  
Alexander Sviridov ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Optical Properties ◽  
Supercritical Co2 ◽  
Cluster Formation ◽  
Mie Scattering ◽  
Density Fluctuations ◽  
Optical Measurements ◽  
Dynamics Simulation ◽  
Ethanol Mixture ◽  
Wide Range

The supercritical CO2 (scCO2) is widely used as solvent and transport media in different technologies. The technological aspects of scCO2 fluid applications strongly depend on spatial–temporal fluctuations of its thermodynamic parameters. The region of these parameters’ maximal fluctuations on the p-T (pressure-temperature) diagram is called Widom delta. It has significant practical and fundamental interest. We offer an approach that combines optical measurements and molecular dynamics simulation in a wide range of pressures and temperatures. We studied the microstructure of supercritical CO2 fluid and its binary mixture with ethanol in a wide range of temperatures and pressures using molecular dynamics (MD) simulation. MD is used to retrieve a set of optical characteristics such as Raman spectra, refractive indexes and molecular refraction and was verified by appropriate experimental measurements. We demonstrated that in the Widom delta the monotonic dependence of the optical properties on the CO2 density is violated. It is caused by the rapid increase of density fluctuations and medium-sized (20–30 molecules) cluster formation. We identified the correlation between cluster parameters and optical properties of the media; in particular, it is established that the clusters in the Widom delta acts as a seed for clustering in molecular jets. MD demonstrates that the cluster formation is stronger in the supercritical CO2-ethanol mixture, where the extended binary clusters are formed; that is, the nonlinear refractive index significantly increased. The influence of the supercritical state in the cell on the formation of supersonic cluster jets is studied using the Mie scattering technique.

scholarly journals The Anomalous Behavior of Thermodynamic Parameters in the Three Widom Deltas of Carbon Dioxide-Ethanol Mixture

2021 ◽  
Vol 22 (18) ◽  
pp. 9813
Author(s):  
Evgenii Igorevich Mareev ◽  
Alexander Petrovich Sviridov ◽  
Vyacheslav Mihailovich Gordienko
Keyword(s):  
Carbon Dioxide ◽  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Thermodynamic Parameters ◽  
Molar Fraction ◽  
Anomalous Behavior ◽  
Density Fluctuations ◽  
Ethanol Mixture ◽  
The Third ◽  
Wide Range

Using molecular dynamics, we demonstrated that in the mixture of carbon dioxide and ethanol (25% molar fraction) there are three pronounced regions on the p-T diagram characterized by not only high-density fluctuations but also anomalous behavior of thermodynamic parameters. The regions are interpreted as Widom deltas. The regions were identified as a result of analyzing the dependences of density, density fluctuations, isobaric thermal conductivity, and clustering of a mixture of carbon dioxide and ethanol in a wide range of pressures and temperatures. Two of the regions correspond to the Widom delta for pure supercritical carbon dioxide and ethanol, while the third region is in the immediate vicinity of the critical point of the binary mixture. The origin of these Widom deltas is a result of the large mixed linear clusters formation.

scholarly journals A method to construct the dynamic landscape of a bio-membrane with experiment and simulation

2022 ◽  
Vol 13 (1) ◽  
Author(s):  
Albert A. Smith ◽  
Alexander Vogel ◽  
Oskar Engberg ◽  
Peter W. Hildebrand ◽  
Daniel Huster
Keyword(s):  
Molecular Dynamics ◽  
Nmr Relaxation ◽  
Dynamics Simulation ◽  
Comprehensive Description ◽  
Correlation Times ◽  
Wide Range ◽  
Dynamic Landscape ◽  
C Nmr ◽  
Analysis Of Motion

AbstractBiomolecular function is based on a complex hierarchy of molecular motions. While biophysical methods can reveal details of specific motions, a concept for the comprehensive description of molecular dynamics over a wide range of correlation times has been unattainable. Here, we report an approach to construct the dynamic landscape of biomolecules, which describes the aggregate influence of multiple motions acting on various timescales and on multiple positions in the molecule. To this end, we use 13C NMR relaxation and molecular dynamics simulation data for the characterization of fully hydrated palmitoyl-oleoyl-phosphatidylcholine bilayers. We combine dynamics detector methodology with a new frame analysis of motion that yields site-specific amplitudes of motion, separated both by type and timescale of motion. In this study, we show that this separation allows the detailed description of the dynamic landscape, which yields vast differences in motional amplitudes and correlation times depending on molecular position.

scholarly journals Molecular dynamics simulation of vacancy cluster formation in β- and α-Si3N4

2020 ◽  
Vol 178 ◽  
pp. 109632
Author(s):  
E. Adabifiroozjaei ◽  
S.S. Mofarah ◽  
H. Ma ◽  
Y. Jiang ◽  
M. Hussein N. Assadi ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Cluster Formation ◽  
Vacancy Cluster ◽  
Dynamics Simulation

scholarly journals Mechanism of asphaltene aggregation induced by supercritical CO2: insights from molecular dynamics simulation

RSC Advances ◽  
2017 ◽  
Vol 7 (80) ◽  
pp. 50786-50793 ◽  
Author(s):  
Bing Liu ◽  
Jiawei Li ◽  
Chao Qi ◽  
Xiaoqi Li ◽  
Tingyi Mai ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Supercritical Co2 ◽  
Selective Extraction ◽  
Dynamics Simulation ◽  
Aggregation Process

Asphaltene was found first separated and then associated in aggregation process due to the selective extraction.

THERMOPHYSICAL PROPERTIES OF URANIUM DIOXIDE: A MOLECULAR DYNAMICS STUDY OF SOLID AND LIQUID PHASES OF STOICHIOMETRIC UO2

2011 ◽  
Vol 25 (23n24) ◽  
pp. 3211-3223 ◽  
Author(s):  
S. D. GÜNAY ◽  
H. B. KAVANOZ ◽  
Ü. AKDERE ◽  
Ç. TAŞSEVEN
Keyword(s):  
Molecular Dynamics ◽  
Transport Properties ◽  
Uranium Dioxide ◽  
Thermophysical Properties ◽  
Good Description ◽  
Model Potential ◽  
Lattice Parameter ◽  
Dynamics Simulation ◽  
Liquid Phases ◽  
Wide Range

Thermodynamic and transport properties of solid and liquid uranium dioxide were studied using classical molecular dynamics simulation, with a newly parametrized interionic model potential. In addition to the static and transport properties which have been previously reported by the authors, this study further confirms that temperature dependence of the calculated thermophysical properties of uranium dioxide are in agreement with the available experimental data at both solid and liquid phases in providing an alternative rigid ion potential to the other model potentials in literature. Although lattice parameter and density have been underestimated, overall results give a fairly good description of the UO 2 system for wide range of temperature (0–4000 K). The transition to the superionic phase, Bredig transition, was successfully observed as a distinct λ-peak in specific heats at about 400 K below the experimental value. The results presented in our previous article and here show that the introduced alternative model potential for uranium dioxide is very promising and we are confident in the success of its use in future studies.

Sign in / Sign up

Export Citation Format

Share Document