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Chemistry

Theoretical chemistry and modeling

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Displaying 151 - 175 of 194

MEASURING PRESSURE AND VACUUM WITH LIGHT: A NEW PHOTONIC, QUANTUM-BASED, PRESSURE STANDARD

September 3, 2015
Author(s)
Jay H. Hendricks, Jacob E. Ricker, Jack A. Stone Jr., Patrick F. Egan, Gregory E. Scace, Gregory F. Strouse, Douglas A. Olson, Donavon Gerty
The future of pressure and vacuum measurement will rely on lasers and Fabry-Perot optical cavities, and will be based on fundamental physics of light interacting with a gas. Light interacts at the quantum level with matter such that light travels at a

In Search of Better Pressure Standards

August 1, 2014
Author(s)
Jay H. Hendricks, Jacob E. Ricker, Patrick F. Egan, Gregory F. Strouse
Based on highly accurate optical interferometry and fundamental quantum calculations, researchers at the National Institute of Standards and Technology (NIST) in the US are developing an improved definition of the SI unit for pressure that will consign the

Measuring order in regioregular poly(3-hexylthiophene) with solid-state 13C CPMAS NMR

January 10, 2014
Author(s)
Ryan C. Nieuwendaal, Chad R. Snyder, Dean M. DeLongchamp
We report on details of molecular packing in high molar mass poly(3-hexylthiophene) (P3HT) by solid-state 13C {1H} cross-polarization magic angle spinning (CPMAS) NMR measurements. The degree of polymer order was estimated for two films of varied drying

Connection between thermodynamics and dynamics of simple fluids in highly attractive pores

October 25, 2013
Author(s)
William P. Krekelberg, Vincent K. Shen, Daniel W. Siderius, Thomas M. Truskett, Jeffrey R. Errington
We investigate the structural and diffusive dynamics properties of a model fluid in highly-absorptive cylindrical pores. At subcritical temperatures, self diffusion displays three distinct regimes as a function of average pore density ρ: 1) a decrease in

Spectra and Relaxation Dynamics of the Pseudohalide (PS) Vibrational Bands for Ru(bpy)2(PS)2 Complexes, PS = CN, NCS and N3

December 5, 2012
Author(s)
Edwin J. Heilweil, Ryan Compton, Helen K. Gerardi, Daniel Weidinger, Douglas J. Brown, Walter J. Dressick, Jeffrey C. Owrutsky
The RuII cyclometalated dye complex, cis-Ru(bpy)2(N3)2 (where bpy = 2,2’-bipyridine), along with two more familiar analogs with pseudohalide (PS) ligands, cis-Ru(bpy)2(NCS)2 and cis-Ru(bpy)2(CN)2, were investigated in solution with static and transient

Impact of surface roughness on diffusion of confined fluids

October 17, 2011
Author(s)
William P. Krekelberg, Vincent K. Shen, Jeffrey R. Errington, Thomas M. Truskett
Using event-driven molecular dynamics simulations, we quantify how the self diffusivity of confined hard-sphere fluids depends on the nature of the confining boundaries. We explore systems with featureless confining boundaries that treat particle-boundary

The sixth industrial fluid properties simulation challenge

July 28, 2011
Author(s)
F Case, Anne M. Chaka, Jonathan D. Moore, Raymond D. Mountain, Richard B. Ross, Vincent K. Shen, Eric A. Stahlberg
The sixth industrial fluid properties simulation challenge was held in 2010. The contestants were challenged to predict mutual solubility in liquid-liquid equilibria (LLE) for the PROGLYDE DMM + water system at various temperatures and atmospheric pressure

Thermochemistry of Ammonium Nitrate, NH4NO3, in the Gas Phase

October 7, 2010
Author(s)
Karl K. Irikura
Hildenbrand and coworkers have shown recently that the vapor above solid ammonium nitrate includes molecules of NH4NO3, not only NH3 and HNO3 as previously believed. Their measurements led to thermochemical values that imply an enthalpy change of D298 = 98

Atomistic Factors Governing Adhesion between Diamond, Amorphous Carbon, and Model Diamond Nanocomposite Surfaces

October 1, 2010
Author(s)
Pamela L. Piotrowski, Rachel J. Cannara, Guangtu Gao, Joseph J. Urban, Robert W. Carpick, Judith A. Harrison
Complementary atomic force microscopy (AFM) and molecular dynamics (MD) simulations were conducted to determine the work of adhesion for diamond(111)(1x1) and diamond(001)(2x1) surfaces paired with other carbon-based materials. In the AFM experiments, the

Kinetics of the Thermal Reaction of H Atoms with Propyne

April 15, 2010
Author(s)
Claudette M. Rosado-Reyes, Jeffrey A. Manion, Wing Tsang
The reaction of hydrogen atoms with propyne(CH≡CCH3) has been investigated in a heated single pulse shock tube at temperatures of 870-1145K and pressures of 2-9 bar. Stable products from various reaction channels (terminal and non-terminal H addition, and

Composition and concentration anomalies for structure and dynamics of Gaussian-core mixtures

August 25, 2009
Author(s)
Vincent K. Shen, Mark J. Pond, William P. Krekelberg, Jeffrey R. Errington, Thomas M. Truskett
We report molecular dynamics simulation results for two-component fluid mixtures of Gaussian-core particles, focusing on how tracer diffusivities and static pair correlations depend on temperature, particle concentration, and composition. At low particle

Scaling Factors and Uncertainties for ab Initio Anharmonic Vibrational Frequencies

August 21, 2009
Author(s)
Russell D. Johnson III, Karl K. Irikura, Raghu N. Kacker, Ruediger Kessel
To predict the vibrational spectra of molecules, ab initio calculations are often used to compute harmonic frequencies, which are usually scaled by empirical factors as an approximate correction for errors in the force constants and for anharmonic effects

The Fifth Industrial Fluid Properties Simulation Challenge

August 5, 2009
Author(s)
F Case, Anne M. Chaka, J Moore, Raymond D. Mountain, J Olson, Richard B. Ross, Martin Schiller, Vincent K. Shen, Eric A. Stahlberg
The fifth industrial fluid properties simulation challenge was held in 2008. In it the contestants were challenged to predict specific, industrially relevant, properties of fluid systems, namely the 1-octanol /water partition coefficient and the infinite

Uncertainties in Scaling Factors for ab Initio Vibrational Zero-Point Energies

March 21, 2009
Author(s)
Karl K. Irikura, Russell D. Johnson III, Raghu N. Kacker, Ruediger Kessel
Vibrational zero-point energies (ZPEs) determined from ab initio calculations are often scaled by empirical factors. An empirical scaling factor partially compensates for the effects arising from vibrational anharmonicity and incomplete treatment of

Standards and Standardization of Molecular Diagnostics

August 15, 2005
Author(s)
J P. Jakupciak, C D. O'Connell
DNA has become a major target for clinical laboratory testing over the past 5 years, and RNA testing is emerging for infectious disease and gene expression (1). To normalize laboratory results across different technology platforms as well as between
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