scholarly journals Glycine in aerosol water droplets: a critical assessment of Köhler theory by predicting surface tension from molecular dynamics simulations

2010 ◽  
Vol 10 (10) ◽  
pp. 23169-23196 ◽  
Author(s):  
X. Li ◽  
T. Hede ◽  
Y. Tu ◽  
C. Leck ◽  
H. Ågren
Keyword(s):  
Molecular Dynamics ◽  
Surface Tension ◽  
Molecular Dynamics Simulations ◽  
Global Climate ◽  
Pure Water ◽  
Model Systems ◽  
Water Droplets ◽  
Cloud Droplets ◽  
Kohler Theory ◽  
Dynamics Simulations

Abstract. Aerosol particles in the atmosphere are important participants in the formation of cloud droplets and have significant impact on cloud albedo and global climate. According to the Köhler theory which describes the nucleation and the equilibrium growth of cloud droplets, the surface tension of an aerosol droplet is one of the most important factors that determine the critical supersaturation of droplet activation. In this paper, with specific interest to remote marine aerosol, we predict the surface tension of aerosol droplets by performing molecular dynamics simulations on two model systems; the pure water droplets and glycine in water droplets. The curvature dependence of the surface tension is interpolated by a quadratic polynomial over the nano-sized droplets and the limiting case of a planar interface, so that the so-called Aitken mode particles which are critical for droplet formation could be covered and the Köhler equation could be improved by incorporating surface tension corrections.

scholarly journals Glycine in aerosol water droplets: a critical assessment of Köhler theory by predicting surface tension from molecular dynamics simulations

2011 ◽  
Vol 11 (2) ◽  
pp. 519-527 ◽  
Author(s):  
X. Li ◽  
T. Hede ◽  
Y. Tu ◽  
C. Leck ◽  
H. Ågren
Keyword(s):  
Molecular Dynamics ◽  
Surface Tension ◽  
Molecular Dynamics Simulations ◽  
Global Climate ◽  
Pure Water ◽  
Model Systems ◽  
Water Droplets ◽  
Cloud Droplets ◽  
Kohler Theory ◽  
Dynamics Simulations

Abstract. Aerosol particles in the atmosphere are important participants in the formation of cloud droplets and have significant impact on cloud albedo and global climate. According to the Köhler theory which describes the nucleation and the equilibrium growth of cloud droplets, the surface tension of an aerosol droplet is one of the most important factors that determine the critical supersaturation of droplet activation. In this paper, with specific interest to remote marine aerosol, we predict the surface tension of aerosol droplets by performing molecular dynamics simulations on two model systems, the pure water droplets and glycine in water droplets. The curvature dependence of the surface tension is interpolated by a quadratic polynomial over the nano-sized droplets and the limiting case of a planar interface, so that the so-called Aitken mode particles which are critical for droplet formation could be covered and the Köhler equation could be improved by incorporating surface tension corrections.

scholarly journals Interface Characteristics of Neat Melts and Binary Mixtures of Polyethylenes from Atomistic Molecular Dynamics Simulations

Polymers ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 1059
Author(s):  
Sanghun Lee ◽  
Curtis W. Frank ◽  
Do Y. Yoon
Keyword(s):  
Molecular Dynamics ◽  
Surface Tension ◽  
Molecular Dynamics Simulations ◽  
Binary Mixtures ◽  
Surface Segregation ◽  
Surface Region ◽  
Polymer Chains ◽  
Methyl Groups ◽  
Free Standing ◽  
Dynamics Simulations

Molecular dynamics simulations of free-standing thin films of neat melts of polyethylene (PE) chains up to C150H302 and their binary mixtures with n-C13H28 are performed employing a united atom model. We estimate the surface tension values of PE melts from the atomic virial tensor over a range of temperatures, which are in good agreement with experimental results. Compared with short n-alkane systems, there is an enhanced surface segregation of methyl chain ends in longer PE chains. Moreover, the methyl groups become more segregated in the surface region with decreasing temperature, leading to the conclusion that the surface-segregation of methyl chain ends mainly arises from the enthalpic origin attributed to the lower cohesive energy density of terminal methyl groups. In the mixtures of two different chain lengths, the shorter chains are more likely to be found in the surface region, and this molecular segregation in moderately asymmetric mixtures in the chain length (C13H28 + C44H90) is dominated by the enthalpic effect of methyl chain ends. Such molecular segregation is further enhanced and dominated by the entropic effect of conformational constraints in the surface for the highly asymmetric mixtures containing long polymer chains (C13H28 + C150H3020). The estimated surface tension values of the mixtures are consistent with the observed molecular segregation characteristics. Despite this molecular segregation, the normalized density of methyl chain ends of the longer chain is more strongly enhanced, as compared with the all-segment density of the longer chain itself, in the surface region of melt mixtures. In addition, the molecular segregation results in higher order parameter of the shorter-chain segments at the surface and deeper persistence of surface-induced segmental order into the film for the longer chains, as compared with those in neat melt films.

Local Order in Aqueous NaCl Solutions and Pure Water:  X-ray Scattering and Molecular Dynamics Simulations Study

2006 ◽  
Vol 110 (46) ◽  
pp. 23515-23523 ◽  
Author(s):  
Salah Bouazizi ◽  
Salah Nasr ◽  
Nejmeddine Jaîdane ◽  
Marie-Claire Bellissent-Funel
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Pure Water ◽  
Local Order ◽  
X Ray ◽  
X Ray Scattering ◽  
Dynamics Simulations ◽  
Ray Scattering

scholarly journals Determining the composition of the vacuum–liquid interface in ionic-liquid mixtures

2018 ◽  
Vol 206 ◽  
pp. 497-522 ◽  
Author(s):  
E. J. Smoll ◽  
M. A. Tesa-Serrate ◽  
S. M. Purcell ◽  
L. D’Andrea ◽  
D. W. Bruce ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Surface Tension ◽  
Ionic Liquid ◽  
Molecular Dynamics Simulations ◽  
Liquid Mixtures ◽  
Liquid Interface ◽  
Liquid Interfaces ◽  
Dynamics Simulations

The vacuum–liquid interfaces of a number of ionic-liquid mixtures have been investigated using a combination of RAS-LIF, selected surface tension measurements, and molecular dynamics simulations.

scholarly journals Use of multiple picosecond high-mass molecular dynamics simulations to predict crystallographic B-factors of folded globular proteins

2016 ◽  
Author(s):  
Yuan-Ping Pang
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Molecular Dynamics Simulations ◽  
Root Mean Square ◽  
A Priori ◽  
Model Systems ◽  
Dynamics Simulation ◽  
High Mass ◽  
Mean Square ◽  
Dynamics Simulations

ABSTRACTPredicting crystallographic B-factors of a protein from a conventional molecular dynamics simulation is challenging in part because the B-factors calculated through sampling the atomic positional fluctuations in a picosecond molecular dynamics simulation are unreliable and the sampling of a longer simulation yields overly large root mean square deviations between calculated and experimental B-factors. This article reports improved B-factor prediction achieved by sampling the atomic positional fluctuations in multiple picosecond molecular dynamics simulations that use uniformly increased atomic masses by 100-fold to increase time resolution. Using the third immunoglobulin-binding domain of protein G, bovine pancreatic trypsin inhibitor, ubiquitin, and lysozyme as model systems, the B-factor root mean square deviations (mean ± standard error) of these proteins were 3.1 ± 0.2–9 ± 1 Å2for Cα and 7.3 ± 0.9–9.6 ± 0.2 Å2for Cγ, when the sampling was done, for each of these proteins, over 20 distinct, independent, and 50-picosecond high-mass molecular dynamics simulations using AMBER forcefield FF12MC or FF14SB. These results suggest that sampling the atomic positional fluctuations in multiple picosecond high-mass molecular dynamics simulations may be conducive toa prioriprediction of crystallographic B-factors of a folded globular protein.

scholarly journals Model HULIS compounds in nanoaerosol clusters – investigations of surface tension and aggregate formation using molecular dynamics simulations

2011 ◽  
Vol 11 (13) ◽  
pp. 6549-6557 ◽  
Author(s):  
T. Hede ◽  
X. Li ◽  
C. Leck ◽  
Y. Tu ◽  
H. Ågren
Keyword(s):  
Molecular Dynamics ◽  
Surface Tension ◽  
Molecular Dynamics Simulations ◽  
Cloud Condensation Nuclei ◽  
Chemical Properties ◽  
Droplet Growth ◽  
Dynamics Simulations ◽  
Pinic Acid ◽  
Vapour Condensation ◽  
And Chemical Properties

Abstract. Cloud condensation nuclei act as cores for water vapour condensation, and their composition and chemical properties may enhance or depress the ability for droplet growth. In this study we use molecular dynamics simulations to show that model humic-like substances (HULIS) in systems containing 10 000 water molecules mimic experimental data well referring to reduction of surface tension. The model HULIS compounds investigated in this study are cis-pinonic acid (CPA), pinic acid (PAD) and pinonaldehyde (PAL). The structural properties examined show the ability for the model HULIS compounds to aggregate inside the nanoaerosol clusters.

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