Robert Hellmann
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View article: Cross Second Virial Coefficients of the N2–H2, O2–H2, and CO2–H2 Systems from First Principles
Cross Second Virial Coefficients of the N2–H2, O2–H2, and CO2–H2 Systems from First Principles Open
The cross second virial coefficients $$B_{12}$$ for interactions of molecular nitrogen (N 2 ) with molecular hydrogen (H 2 ), of molecular oxygen (O 2 ) with H 2 , and of carbon dioxide (CO 2 ) with H 2 were obtained at temperatures ra…
View article: Speed of sound measurements and derived third and fourth acoustic virial coefficients of supercritical neon
Speed of sound measurements and derived third and fourth acoustic virial coefficients of supercritical neon Open
We report comprehensive and accurate measurements of the speed of sound in neon. These measurements were carried out by a double-path-length pulse-echo technique and cover the temperature range between 200 K and 420 K with pressures up to …
View article: <i>Ab initio</i> potential energy surfaces for the O2–O2 system and derived thermophysical properties
<i>Ab initio</i> potential energy surfaces for the O2–O2 system and derived thermophysical properties Open
New intermolecular potential energy surfaces (PESs) for the quintet, triplet, and singlet states of two rigid oxygen (O2) molecules in their triplet ground electronic states were developed. Quintet interaction energies were obtained for 89…
View article: <i>Ab Initio</i> Calculation of Fluid Properties for Precision Metrology
<i>Ab Initio</i> Calculation of Fluid Properties for Precision Metrology Open
Recent advances regarding the interplay between ab initio calculations and metrology are reviewed, with particular emphasis on gas-based techniques used for temperature and pressure measurements. Since roughly 2010, several thermophysical …
View article: Cross Second Virial Coefficients of the H<sub>2</sub>O–H<sub>2</sub> and H<sub>2</sub>S–H<sub>2</sub> Systems from First-Principles
Cross Second Virial Coefficients of the H<sub>2</sub>O–H<sub>2</sub> and H<sub>2</sub>S–H<sub>2</sub> Systems from First-Principles Open
The cross second virial coefficients B12 for the interactions of water (H2O) with molecular hydrogen (H2) and of hydrogen sulfide (H2S) with H2 were obtained at temperatures in the range from 150 to 2000 K from new intermolecular potential…
View article: Determination of the Binary Diffusion Coefficients and Interaction Viscosities of the Systems Carbon Dioxide–Nitrogen and Ethane–Methane in the Dilute Gas Phase from Accurate Experimental Viscosity Data Using the Kinetic Theory of Gases
Determination of the Binary Diffusion Coefficients and Interaction Viscosities of the Systems Carbon Dioxide–Nitrogen and Ethane–Methane in the Dilute Gas Phase from Accurate Experimental Viscosity Data Using the Kinetic Theory of Gases Open
The results of viscosity measurements at moderate densities on the two gaseous mixtures carbon dioxide–nitrogen and ethane–methane including the pure gases between 253.15 K and 473.15 K, originally performed by Humberg et al. at Ruhr Unive…
View article: Determination of the binary diffusion coefficients and interaction viscosities of the systems carbon dioxide-nitrogen and ethane-methane in the dilute gas phase from accurate experimental viscosity data using the kinetic theory of gases
Determination of the binary diffusion coefficients and interaction viscosities of the systems carbon dioxide-nitrogen and ethane-methane in the dilute gas phase from accurate experimental viscosity data using the kinetic theory of gases Open
The results of viscosity measurements at moderate densities on the two gaseous mixtures carbon dioxide-nitrogen and ethane-methane including the pure gases between 253.15 K and 473.15 K, originally performed by Humberg et al. at Ruhr Unive…
View article: Ab initio Calculation of Fluid Properties for Precision Metrology
Ab initio Calculation of Fluid Properties for Precision Metrology Open
Recent advances regarding the interplay between ab initio calculations and metrology are reviewed, with particular emphasis on gas-based techniques used for temperature and pressure measurements. Since roughly 2010, several thermophysical …
View article: Cross Second Virial Coefficient of the H2O–CO System from a New Ab Initio Pair Potential
Cross Second Virial Coefficient of the H2O–CO System from a New Ab Initio Pair Potential Open
The cross second virial coefficient $$B_{12}$$ for the interaction between water (H 2 O) and carbon monoxide (CO) was obtained with low uncertainty at temperatures from 200 K to 2000 K employing a new intermolecular potential energy su…
View article: First‐Principles Diffusivity Ratios for Atmospheric Isotope Fractionation on Mars and Titan
First‐Principles Diffusivity Ratios for Atmospheric Isotope Fractionation on Mars and Titan Open
Recent work used the kinetic theory of molecular gases, along with state‐of‐the‐art intermolecular potentials, to calculate from first principles the diffusivity ratios necessary for modeling kinetic fractionation of water isotopes in air.…
View article: First‐Principles Diffusivity Ratios for Kinetic Isotope Fractionation of Water in Air
First‐Principles Diffusivity Ratios for Kinetic Isotope Fractionation of Water in Air Open
Kinetic isotope fractionation between water vapor and liquid water or ice depends on the ratio of the diffusivities of the isotopic species in air, but there is disagreement as to the values of these ratios and limited information about th…
View article: Zero-Density Limit of the Residual Entropy Scaling of Transport Properties
Zero-Density Limit of the Residual Entropy Scaling of Transport Properties Open
The modified residual entropy scaling approach has been shown to be a successful means of scaling dense phase transport properties. In this work, we investigate the dilute-gas limit of this scaling. This limit is considered for model poten…
View article: Influence of a magnetic field on the viscosity of a dilute gas consisting of linear molecules
Influence of a magnetic field on the viscosity of a dilute gas consisting of linear molecules Open
The viscomagnetic effect for two linear molecules, N2 and CO2, has been calculated in the dilute-gas limit directly from the most accurate ab initio intermolecular potential energy surfaces presently available. The calculations were perfor…