scholarly journals Structure and Properties of High and Low Free Volume Polymers Studied by Molecular Dynamics Simulation

Computation ◽  
2019 ◽  
Vol 7 (2) ◽  
pp. 27 ◽  
Author(s):  
Mikhail Mazo ◽  
Nikolay Balabaev ◽  
Alexandre Alentiev ◽  
Ivan Strelnikov ◽  
Yury Yampolskii
Keyword(s):  
Molecular Dynamics ◽  
Free Volume ◽  
Chemical Nature ◽  
Glassy Polymers ◽  
Dynamics Simulation ◽  
Size Distributions ◽  
Structure And Properties ◽  
Delaunay Tessellation ◽  
Accessible Volume ◽  
Probe Size

Using molecular dynamics, a comparative study was performed of two pairs of glassy polymers, low permeability polyetherimides (PEIs) and highly permeable Si-containing polytricyclononenes. All calculations were made with 32 independent models for each polymer. In both cases, the accessible free volume (AFV) increases with decreasing probe size. However, for a zero-size probe, the curves for both types of polymers cross the ordinate in the vicinity of 40%. The size distribution of free volume in PEI and highly permeable polymers differ significantly. In the former case, they are represented by relatively narrow peaks, with the maxima in the range of 0.5–1.0 Å for all the probes from H2 to Xe. In the case of highly permeable Si-containing polymers, much broader peaks are observed to extend up to 7–8 Å for all the gaseous probes. The obtained size distributions of free volume and accessible volume explain the differences in the selectivity of the studied polymers. The surface area of AFV is found for PEIs using Delaunay tessellation. Its analysis and the chemical nature of the groups that form the surface of free volume elements are presented and discussed.

An Insight into Solubility of H2S in Choline Based Ionic Liquids from Molecular Dynamics Simulation

2020 ◽  
Vol 17 (2) ◽  
pp. 1422-1431
Author(s):  
Fitri Norizatie Mohd Salehin ◽  
Khairulazhar Jumbri ◽  
Anita Ramli ◽  
Shaari Daud
Keyword(s):  
Molecular Dynamics ◽  
Free Energy ◽  
Free Volume ◽  
Chemical Potential ◽  
Alkyl Chain ◽  
Solvation Free Energy ◽  
Volume Effect ◽  
Dynamics Simulation ◽  
Percentage Error ◽  
Molar Density

Solvation free energy of six choline based ILs were computed under molecular dynamics (MD) simulation using Bennet Acceptance Ratio (BAR) method. H2S removal from the natural gas can be accomplished by absorption process using a solvent. Degree elimination of gases in liquid can be estimated by excess chemical potential (μex), Henry’s law constant (kH), enthalpy (hex), and entropy (sex). The Optimised Potential Liquids Simulation (OPLS) force fields used for ILs were validated against experimental density in order to get valid results of solvation free energy. The percentage error of the predicted density of six choline based ILs were below than 2.0% which is a good agreement with the previous study. The highest value of kH was 109.23 atm gained by choline thiocyanate [Chl][tcy] and the lowest value of kH was 23.25 atm obtained by choline acetate [Chl][act]. There are many features that influence the solubility of H2S for example length of alkyl chain, free volume effect, molar density, type of anions and hydrogen bonding interaction. In order to understand the behaviour of H2S molecules in ILs system, the radial distribution function (RDF) of H2S-ILs and RDF for specific atom were analysed. Basically, the shorter the alkyl chain, increase in molar density of ILs, reduce the free volume thus provide less space for H2S to occupy and decrease insolubility.

Structure and Properties of the GeAsS Glasses from Ab initio Calculations

2014 ◽  
Vol 1035 ◽  
pp. 502-507
Author(s):  
Li An Chen
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Ab Initio ◽  
Bond Angle ◽  
Distribution Functions ◽  
Dynamics Simulation ◽  
Angle Distribution ◽  
Structure And Properties ◽  
Bond Angle Distribution ◽  
Pair Distribution Functions

The structure and properties of the GexAsxS100-2x have been studied by ab initio molecular dynamics simulation. By calculating the pair distribution functions, bond angle distribution functions, we analyze the structure and properties of the alloys. Calculations show that Ge and As are all well combined with S atoms. When x is smaller than 25.0 the binding increases with x , when x is larger than 25.0 the binding decreases with increasing x . The intervention of As atom does not affect the GeS2 formation in Ge40As40S80

scholarly journals Methods for the calculation of occupied volumes in glassy polymers: The lattice integration and the monte carlo methods

2003 ◽  
Vol 1 (4) ◽  
pp. 402-426 ◽  
Author(s):  
E. Rozhkov ◽  
B. Schukin ◽  
I. Ronova
Keyword(s):  
Monte Carlo ◽  
Error Estimates ◽  
Free Volume ◽  
Monte Carlo Methods ◽  
Glassy Polymer ◽  
Monomer Unit ◽  
Glassy Polymers ◽  
Inert Gases ◽  
Improved Method ◽  
Accessible Volume

AbstractA new model for characterizing the free volume of a glassy polymer—gas systems is proposed. An improved method for the calculation of occupied volume per monomer unit was developed within the limits of this model. The model assumptions, error estimates and algorithm efficiencies are described. Using the example of polyvinyltrimethylsilane, it is shown that linear dependences of logarithms of the diffusion and the permeability coefficients on specific accessible volume for inert gases exist.

Free Volume Distribution in Polymer Liquid and Glass Evaluated by Molecular Dynamics Simulation

1990 ◽  
Vol 215 ◽  
Author(s):  
R. J. Roe ◽  
D. Rigby
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Free Volume ◽  
Hard Spheres ◽  
Voronoi Tessellation ◽  
Dynamics Simulation ◽  
Volume Distribution ◽  
Chain Molecules ◽  
Polymer Liquid ◽  
Shape And Size

AbstractMolecular dynamics simulation has been performed with dense systems of alkane-like chain molecules. Distribution of occupied and unoccupied space in the system was then evaluated by the technique of Voronoi tessellation of space and by enumeration of the cavities formed when hard spheres of diameter D were assumed placed on atomic centers. The distribution of cavity volumes is extremely broad and often exhibits a bimodal or trimodal character. These cavities change shape and size with time even at temperatures much below Tg.

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