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Chemistry

Theoretical chemistry & modeling

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Displaying 101 - 125 of 184

Effects of Nitrogen on the Interface Density of States Distribution in 4H-SiC Metal Oxide Semiconductor Field Effect Transistors: Super-hyperfine Interactions and Near Interface Silicon Vacancy Energy Levels

November 13, 2018
Author(s)
Mark Anders, Patrick M. Lenahan, Arthur H. Edwards, Peter A. Schultz, Renee M. Van Ginhoven
The performance of SiC-based metal-oxide-semiconductor field-effect transistors (MOSFETs) is greatly enhanced by a post oxidation anneal in NO. These anneals greatly improve effective channel mobilities and substantially decrease interface trap densities

Polymorphism and thermophysical properties of L- and DL-menthol

November 5, 2018
Author(s)
Vojtech Stejfa, Ala Bazyleva, Michal Fulem, Jan Rohlicek, Eliska Skorepova, Kvetoslav Ruzicka, Andrey V. Blokhin
The thermodynamic properties, phase behavior, and kinetics of polymorph transformations of racemic (DL-) and enantiopure (L-) menthol were studied using a combination of advanced experimental techniques, including static vapor pressure measurements

Thermodynamic Properties of Organic Substances: Experiment, Modeling, and Technological Applications

October 26, 2018
Author(s)
Gennady J. Kabo, Andrey V. Blokhin, Eugene Paulechka, Gennady N. Roganov, Michael D. Frenkel, Iosif A. Yursha, Vladimir Diky, Dzmitry H. Zaitsau, Ala Bazyleva, Vladimir V. Simirsky, Larisa Karpushenkava, Viktor M. Sevruk
In this review, results of the studies of thermodynamic properties of organic substances conducted at the Chemistry Department of the Belarusian State University (Minsk, Belarus) over a period of more than 50 years are summarized. Emphasis is made on

Complex coacervation in polyelectrolytes from a coarse-grained model

August 22, 2018
Author(s)
Vivek M. Prabhu, Marat Andreev, Jian Qin, Matthew Tirrell, Juan J. de Pablo, Jack F. Douglas
Polyelectrolyte coacervation refers to the formation of distinct liquid phases that arise when polyelectrolytes of opposite charge are mixed under appropriate polymer and salt concentrations. Molecular-level studies of complex polyelectrolyte coacervation

A Spin-1 Representation for Dual-Funnel Energy Landscapes

July 20, 2018
Author(s)
Justin E. Elenewski, Kirill Velizhanin, Michael P. Zwolak
The interconversion between left- and right-handed helical folds of a polypeptide defines a dual-funneled free energy landscape. In this context, the funnel minima are connected through a continuum of unfolded conformations, evocative of the classical

Polyelectrolyte association and solvation

July 10, 2018
Author(s)
Alexandros Chremos, Jack F. Douglas
There has been significant interest in the tendency of highly charged particles having the same charge to form dynamic clusters in solution, but an accepted theoretical framework that can account for this ubiquitous phenomenon has been slow to develop. The

Design and Implementation of pyPRISM: A Polymer Liquid-State Theory Framework

June 15, 2018
Author(s)
Tyler B. Martin, Thomas E. Gartner, Ronald L. Jones, Chad R. Snyder, Arthi Jayaraman
Polymer Reference Interaction Site Model (PRISM) theory describes the equilibrium spatial- correlations, thermodynamics, and structure of liquid- like polymer systems and macromolecular materials. Here, we describe the code structure, implementation, and

Energy Renormalization Method for the Coarse-Graining of Polymer Viscoelasticity

May 10, 2018
Author(s)
Jake Song, David D. Hsu, Kenneth R. Shull, Frederick R. Phelan Jr., Jack F. Douglas, Wenjie Xia, Sinan Keten
Developing time and temperature transferable coarse-grained (CG) models is essential for the computational prediction and design of polymeric glass-forming materials, but this goal has remained elusive. The dynamics of CG models are often greatly altered

Development and Validation of a Mechanism for Flame Propagation in R-32/Air Mixtures

March 6, 2018
Author(s)
Donald R. Burgess Jr., Jeffrey A. Manion, Robert R. Burrell, Valeri I. Babushok, Michael Hegetschweiler, Gregory T. Linteris
A mechanism for the combustion of the refrigerant R-32 (CH2F2) in air mixtures was developed and validated through comparisons with measured flame speeds for a range of equivalence ratios (0.9 to 1.4) and pressures (1 to 3 bar) using a constant-volume

Quantum for Pressure

January 5, 2018
Author(s)
Jay H. Hendricks, Patrick F. Egan, Jacob E. Ricker, Jack A. Stone Jr., Kevin O. Douglass, Gregory F. Strouse
A team of NIST scientists is working to fundamentally change the way that the unit of pressure is realized and disseminated, an effort that will lead to the elimination of mercury barometer pressure standards.

The Influence of the Aromaticity in the Gas Chromatography Retention: The Case of Polycyclic Aromatic Sulfur Heterocycles

December 15, 2017
Author(s)
Jorge O. Ona-Ruales, Yosadara Ruiz-Morales, Fernando Alvarez-Ramirez, Walter Brent Wilson, Stephen A. Wise
The aromaticity has been used as a criterion to explain the GC retention of cata-condensed polycyclic aromatic sulfur heterocycles (PASHs) C12H8S, C16H10S, C20H12S; and peri-condensed PASHs C18H10S, in a GC column with 50% phenyl / 50% methyl silphenylene

Free Surface Relaxations of Star-Shaped Polymer Films

November 28, 2017
Author(s)
Alexandros Chremos, Bradley R. Frieberg, Emmanouil Glynos, Kyle Johnson, Hengxi Yang, Suresh Narayanan, Peter F. Green, Georgios Sakellariou
X-ray photon correlation spectroscopy (XPCS) studies show that the viscosities of thin film linear chain polymers at temperatures sufficiently high above the bulk glass transition temperature Tg bulk are equal to the bulk zero shear viscosities. The free

Electrochemical capacitance of CO-terminated Pt(111) is dominated by CO-solvent gap

October 17, 2017
Author(s)
Ravishankar Sundararaman, Marta C. Figueiredo, Marc Koper, Kathleen Schwarz
The distribution of electric fields within the electrochemical double layer depends on both the electrode and electrolyte in complex ways. These fields strongly influence chemical dynamics in the electrode-electrolyte interface, but cannot be measured

Simulation-aided Correlations for the Dielectric Constant of H2S, SO2, and SF6

August 16, 2017
Author(s)
Allan H. Harvey, Raymond D. Mountain
A new method is developed for correlating the static dielectric constant of polar fluids over wide ranges of conditions where few experimental data exist. Molecular dynamics simulations are used to establish the temperature and density dependence of the

Temperature extrapolation of multicomponent grand canonical free energy landscapes

August 7, 2017
Author(s)
Nathan Mahynski, Jeffrey R. Errington, Vincent K. Shen
We derive a method for extrapolating the grand canonical free energy landscape of a multicomponent fluid system from one temperature to another. Previously, we introduced this statistical mechanical framework for the case where kinetic energy contributions

Connection between thermodynamics and dynamics of simple fluids in pores: impact of fluid-fluid interaction range and fluid-solid interaction strength

July 5, 2017
Author(s)
William P. Krekelberg, Daniel W. Siderius, Vincent K. Shen, Thomas M. Truskett, Jeffrey R. Errington
Using molecular simulations, we investigate how the range of fluid-fluid (adsorbate-adsorbate) interactions and the strength of fluid-solid (adsorbate-adsorbent) interactions impact the strong connection between distinct adsorptive regimes and distinct
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