Atomistic Simulation of Polymer Melt Elasticity:  Calculation of the Free Energy of an Oriented Polymer Melt

1998 ◽  
Vol 31 (18) ◽  
pp. 6310-6332 ◽  
Author(s):  
Vlasis G. Mavrantzas ◽  
Doros N. Theodorou
Keyword(s):  
Free Energy ◽  
Atomistic Simulation ◽  
Polymer Melt ◽  
Oriented Polymer ◽  
Melt Elasticity

scholarly journals Neural networks-based variationally enhanced sampling

2019 ◽  
Vol 116 (36) ◽  
pp. 17641-17647 ◽  
Author(s):  
Luigi Bonati ◽  
Yue-Yu Zhang ◽  
Michele Parrinello
Keyword(s):  
Neural Networks ◽  
Free Energy ◽  
Atomistic Simulation ◽  
Sampling Method ◽  
Machine Learning Techniques ◽  
Enhanced Sampling ◽  
Collective Variables ◽  
Learning Techniques ◽  
Minimization Technique ◽  
Energy Surfaces

Sampling complex free-energy surfaces is one of the main challenges of modern atomistic simulation methods. The presence of kinetic bottlenecks in such surfaces often renders a direct approach useless. A popular strategy is to identify a small number of key collective variables and to introduce a bias potential that is able to favor their fluctuations in order to accelerate sampling. Here, we propose to use machine-learning techniques in conjunction with the recent variationally enhanced sampling method [O. Valsson, M. Parrinello, Phys. Rev. Lett. 113, 090601 (2014)] in order to determine such potential. This is achieved by expressing the bias as a neural network. The parameters are determined in a variational learning scheme aimed at minimizing an appropriate functional. This required the development of a more efficient minimization technique. The expressivity of neural networks allows representing rapidly varying free-energy surfaces, removes boundary effects artifacts, and allows several collective variables to be handled.

The rmomechanical properties of fibre produced from a pre-oriented polymer melt

1976 ◽  
Vol 8 (3) ◽  
pp. 305-306
Author(s):  
V. V. Krenev ◽  
V. G. Baranov ◽  
S. Ya. Frenkel
Keyword(s):  
Polymer Melt ◽  
Oriented Polymer

An approach to the estimation of polymer melt elasticity

1984 ◽  
Vol 23 (6) ◽  
pp. 608-616 ◽  
Author(s):  
A. V. Shenoy ◽  
D. R. Saini
Keyword(s):  
Polymer Melt ◽  
Melt Elasticity

Visualisation of the structure transfer between an oriented polymer melt and the semi-crystalline state

Polymer ◽  
2005 ◽  
Vol 46 (8) ◽  
pp. 2579-2583 ◽  
Author(s):  
Norbert Stribeck ◽  
Rüdiger Bayer ◽  
Peter Bösecke ◽  
Armando Almendarez Camarillo
Keyword(s):  
Crystalline State ◽  
Polymer Melt ◽  
Oriented Polymer

scholarly journals Predicting Chemical Reaction Equilibrium in Dilute Solutions by Atomistic Simulation: Application to CO2 Reactive Absorption in Aqueous Primary Alkanolamine Solutions

2020 ◽  
Author(s):  
Javad Noroozi ◽  
William Smith
Keyword(s):  
Free Energy ◽  
Atomistic Simulation ◽  
Equilibrium Constants ◽  
Ideal Gas ◽  
Free Energy Calculations ◽  
Primary Amines ◽  
Dilute Solutions ◽  
Energy Calculations ◽  
Reactive Absorption ◽  
Reaction Equilibrium

We present a general atomistic simulation framework for efficient reactive equilibrium calculations in dilute solutions, and its application to CO2 reactive absorption in aqueous alkanolamine solutions. No experimental data of any kind for the solvents is required and no empirical adjustments are required for its implementation. This hybrid methodology involves calculating the required reaction equilibrium constants by combining high–level quantum chemical calculations of ideal–gas standard reaction Gibbs energies (∆G0 ) with conventional free energy calculations for transfer of the molecular species from the ideal gas to infinite dilution in the solvent (i.e, their solvation free energies). For the solvation free energy calculations, we use explicit solvent molecular dynamics simulations with the General AMBER Force Field (GAFF). The resulting equilibrium constants are then coupled with a macroscopic Henry–Law–based ideal solution model to calculate the solution speciation and the CO2 partial pressure, PCO2 . We show results for seven primary amines: monoethanolamine (MEA), 2–amino–2–methylpropanol (AMP), 1–amino–2– propanol (1–AP), 2–amino–2–methyl–1,3–propanediol (AMPD), 2–aminopropane–1,3– diol (SAPD), 2–(2–aminoethoxy)ethanol (2–AEE) or diglycolamine (DGA), and 2– amino–1–propanol (2–AP). Experimental speciation and PCO2 data for some of these is available, with which we validate our methodology. We predict new results for others in cases when such data is unavailable, and provide explanations for the experimental inability to detect carbamate species in some cases. Our results for the pK value of the carbamate reversion reaction are within the chemical accuracy limit of 218.506/T in comparison with experiment when such data exist, which at 298.15 K corresponds to 0.73 pK units. We argue that the precision of our pK predictions in general is comparable to that which can be obtained from conventional experimental methodologies for these quantities. Our results suggest that the presented molecular simulation methodology may provide a robust and cost–efficient tool for solvent screening in the design of post–combustion CO2 capture processes.<br>

Grafting of metallocene copolymer to higher polarity with acrylic acid

2019 ◽  
Vol 106 ◽  
pp. 16-21
Author(s):  
IGOR NOVAK ◽  
JURAJ PAVLINEC ◽  
IVAN CHODÁK ◽  
ANGELA KLEINOVÁ ◽  
JOZEF PREŤO ◽  
...  
Keyword(s):  
Free Energy ◽  
Acrylic Acid ◽  
Surface Free Energy ◽  
Polymer Melt ◽  
Adhesive Properties ◽  
Grafting Efficiency ◽  
The Creation

Grafting of metallocene ethyle-octene copolymer to higher polarity with acrylic acid. Metallocene polyolefins (MePO) were grafted in melt due to increasing their surface free energy and adhesive properties. MePO modification with ozone was used to initiate the creation of peroxides on the surface ofthe polymer with subsequently grafting of acrylic acid in polymer melt. The grafting efficiency of grafting in melt is high and varies between 0.77 and 0.97.

A method for calculating the nonequilibrium entropy of a flowing polymer melt via atomistic simulation

2021 ◽  
Vol 155 (11) ◽  
pp. 111101
Author(s):  
Brian J. Edwards ◽  
M. Hadi Nafar Sefiddashti ◽  
Bamin Khomami
Keyword(s):  
Atomistic Simulation ◽  
Polymer Melt ◽  
Nonequilibrium Entropy

TRANSFER OF A POLLUTANT MOLECULE THROUGH A WATER FILM SUPPORTED BY MgO(100): FREE ENERGY PROFILES

1999 ◽  
Vol 06 (06) ◽  
pp. 1265-1274 ◽  
Author(s):  
C. TOUBIN ◽  
S. PICAUD ◽  
P. N. M. HOANG ◽  
C. GIRARDET ◽  
R. M. LYNDEN-BELL
Keyword(s):  
Free Energy ◽  
Transfer Process ◽  
Atomistic Simulation ◽  
Water Film ◽  
Intermolecular Potentials ◽  
Substrate Interface ◽  
Energy Profiles ◽  
Mgo Substrate ◽  
Free Energy Profiles ◽  
Water Water Water

We have determined the free energy profiles for some pollutant molecules (HCl, HOCl and CO 2) entering and crossing a water film supported on a MgO substrate. This was done by using atomistic simulation with models for the pollutant–water, water–water, water–substrate and pollutant–substrate intermolecular potentials. Our aim is to establish these profiles in order to provide a foundation for the understanding of the kinetic processes of pollution on a water-covered surface. We show that the water–substrate interface gives rise to two mimima in the free energy profiles and influence strongly the transfer process.

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