Solvent flow patterns fluctuating largely around a protein and correlation with solvent density fluctuations: A molecular dynamics study

2010 ◽  
Vol 132 (15) ◽  
pp. 155103 ◽  
Author(s):  
Koji Umezawa ◽  
Ryota Morikawa ◽  
Haruki Nakamura ◽  
Junichi Higo
Keyword(s):  
Molecular Dynamics ◽  
Flow Patterns ◽  
Density Fluctuations ◽  
Solvent Density ◽  
Solvent Flow

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.

Role of density fluctuations in the solvation structure in supercritical dilute solutions: a molecular dynamics study

1996 ◽  
Vol 125 (1-2) ◽  
pp. 1-11 ◽  
Author(s):  
Masahiko Katagiri ◽  
Minoru Tanaka ◽  
Hiromitsu Takaba ◽  
Akira Miyamoto ◽  
Yasuo Nozue ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Density Fluctuations ◽  
Dilute Solutions ◽  
Solvation Structure
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