Surface roughness stabilizes the clustering of self-propelled triangles
Self-propelled particles can spontaneously form dense phases from a dilutesuspension in a process referred to as motility-inducedphase separation. The properties of the out-of-equilibrium structures that are formed are governed by the specifics of the particle interactions and the strength of the activity. Thus far, most studies into the formation of these structures have focused on sphericalcolloids, dumbbells, and rod-like particles endowed with various interaction potentials. Only a few studies have examined the collective behavior of more complex particle shapes. Here, we increase the geometric complexity and use molec...
Source: Journal of Chemical Physics - October 5, 2016 Category: Physics Authors: Sven Erik Ilse, Christian Holm and Joost de Graaf Source Type: research
Diffusion of helical particles in the screw-like nematic phase
The mechanism ofdiffusion of helical particles in the new screw-likenematic phase is studied by molecular dynamics numerical simulation. Several dynamical indicators have reported that evidence and microscopically characterise the special translo-rotationalmotion by which helical particles move in thischiralliquid-crystalline phase. Besides mean square displacements anddiffusion coefficients resolvedparallel and perpendicular to the nematic director, a suitable translo-rotational van Hove self-correlation function and a sequence of translational and rotational velocity, self- and distinct-, timecorrelation functions are ca...
Source: Journal of Chemical Physics - October 5, 2016 Category: Physics Authors: Giorgio Cinacchi, Alberto Maria Pintus and Alessandro Tani Source Type: research
The behavior of active diffusiophoretic suspensions: An accelerated Laplacian dynamics study
Diffusiophoresis is the process by which a colloidal particle moves in response to the concentration gradient of a chemical solute. Chemically active particles generate solute concentration gradients via surface chemical reactions which can result in their own motion — the self-diffusiophoresis of Janus particles — and in the motion of other nearby particles — normal down-gradient diffusiophoresis. The long-range nature of the concentration disturbance created by a reactive particle results in strong interactions among particles and can lead to the formati on of clusters and even coexisting dense and dilute regions o...
Source: Journal of Chemical Physics - October 5, 2016 Category: Physics Authors: Wen Yan and John F. Brady Source Type: research
Ionic profiles close to dielectric discontinuities: Specific ion-surface interactions
We study, by incorporating short-range ion-surface interactions, ionic profiles ofelectrolytesolutions close to a non-charged interface between twodielectric media. In order to account for important correlation effects close to the interface, the ionic profiles are calculated beyondmean-fieldtheory, using the loop expansion of thefree energy. We show that how it is possible to overcome the well-known deficiency of the regular loop expansion close to thedielectric jump and treat the non-linear boundary conditions within the framework of field theory. The ionic profiles are obtained analytically to one-loop order in thefree ...
Source: Journal of Chemical Physics - October 5, 2016 Category: Physics Authors: Tomer Markovich, David Andelman and Henri Orland Source Type: research
Pressure-dependent morphology of trihexyl(tetradecyl)phosphonium ionic liquids: A molecular dynamics study
In the presentmolecular dynamics study, we investigate the effects of increasingpressure on thestructural morphology of trihexyl(tetradecyl)phosphonium bromide (P666,14+/Br−) and trihexyl(tetradecyl)phosphonium dicyanamide (P666,14+/DCA−)ionic liquids (ILs). Special attention was paid to how charge and polarity orderings, which are present in the microscopicstructure of these ILs at ambient conditions, respond to very high externalpressure. The simulatedX-ray scatteringstructure functions, S(q)s, of the two systems reveal that both the characteristic orderings show appreciable responsiveness towards the appliedpressure...
Source: Journal of Chemical Physics - October 5, 2016 Category: Physics Authors: Shobha Sharma, Aditya Gupta, Debdas Dhabal and Hemant K. Kashyap Source Type: research
Structure and dynamics of binary liquid mixtures near their continuous demixing transitions
The dynamic and static critical behavior of a family of binary Lennard-Jones liquid mixtures, close to their continuous demixing points (belonging to the so-calledmodelH′ dynamic universality class), are studied computationally by combining semi-grand canonicalMonte Carlo simulations and large-scalemolecular dynamics (MD) simulations, accelerated by graphic processing units (GPU). The symmetric binary liquid mixtures considered cover a variety of densities, a wide range of compressibilities, and various interactions between the unlike particles. The static quantities studied here encompass the bulkphase diagram (includin...
Source: Journal of Chemical Physics - October 5, 2016 Category: Physics Authors: Sutapa Roy, S. Dietrich and Felix H öfling Source Type: research
Ordering effects of conjugate thermal fields in simulations of molecular liquids: Carbon dioxide and water
As shown previously, it is possible to apply configurational and kinetic thermostats simultaneously in order to induce a steady thermal flux inmolecular dynamics simulations of many-particle systems. This flux appears to promote motion along potential gradients and can be utilized to enhance the sampling of ordered arrangements, i.e., it can facilitate the formation of a critical nucleus. Here we demonstrate that the same approach can be applied to molecular systems, and report a significant enhancement of the homogeneous crystalnucleation of acarbon dioxide (EPM2 model) system. Quantitative ordering effects and reduction ...
Source: Journal of Chemical Physics - October 5, 2016 Category: Physics Authors: Harro R. Dittmar and Peter G. Kusalik Source Type: research
Thermodiffusion, molecular diffusion and Soret coefficients of aromatic+n-alkane binary mixtures
In the present work, we havemeasured the thermodiffusion coefficient of 51 binary liquid mixtures at 25oC. These mixtures correspond to the series of the aromatics toluene and 1-methylnaphthalene with n-alkanesnCi (i = 6, 8, 10, 12, and 14) at different mass fractions in the whole range. For that, we have used the thermogravitational technique. It is shown that the thermodiffusion coefficient is a linear function of the mass fraction in all the mixtures. Extrapolating the lines, we obtain the thermodiffusion coefficient in dilutesolutions of n-alkanes for both toluene and 1-methylnaphthalene. These limiting values show a l...
Source: Journal of Chemical Physics - October 5, 2016 Category: Physics Authors: Miren Larra ñaga, M. Mounir Bou-Ali, Estela Lapeira, Ion Lizarraga and Carlos Santamaría Source Type: research
Intermolecular associations in an equimolar formamide-water solution based on neutron scattering and DFT calculations
In the present work, we have investigated the intermolecular associations of formamide withwater in an equimolar formamide-watersolution (FA-Water) by means ofneutron scattering in combination withdensity functional theory calculations. Theneutron scattering data were analyzed to deduce thestructure factor SM(q) and the intermolecular paircorrelation function gL(r). By considering different hydrogen bonded FA-Water associations, it has been shown that some of them describe well the local order in thesolution. Natural bond orbital and atoms in molecules analyses have been performed to give more insight into the properties o...
Source: Journal of Chemical Physics - October 5, 2016 Category: Physics Authors: Hafedh Abdelmoulahi, Houcine Ghalla, Salah Nasr, Jacques Darpentigny and Marie-Claire Bellissent-Funel Source Type: research
Dynamics of proteins aggregation. I. Universal scaling in unbounded media
It is well understood that in some casesproteins do not fold correctly and, depending on their environment, even properly-foldedproteins change their conformation spontaneously, taking on a misfolded state that leads toproteinaggregation and formation of large aggregates. An important factor that contributes to theaggregation is theinteractions between the misfoldedproteins. Depending on theaggregation environment, the aggregates may take on various shapes forming larger structures, such asprotein plaques that are often toxic. Their deposition in tissues is a major contributing factor to many neuro-degenerative diseases, s...
Source: Journal of Chemical Physics - October 5, 2016 Category: Physics Authors: Size Zheng, Leili Javidpour, Katherine S. Shing and Muhammad Sahimi Source Type: research
The intermolecular interaction in D2 − CX4 and O2 − CX4 (X = F, Cl) systems: Molecular beam scattering experiments as a sensitive probe of the selectivity of charge transfer component
Gas phase collisions of a D2 projectile by CF4 and by CCl4 targets have been investigated with the molecularbeam technique. The integral cross section,Q, has beenmeasured for both collisional systems in the thermal energy range and oscillations due to the quantum “glory” interference have been resolved in the velocity dependence ofQ. Theanalysis of themeasuredQ(v) data provided novel information on theanisotropic potential energy surfaces of the studied systems at intermediate and large separation distances. The relative role of the most relevant types of contributions to the globalinteraction has been characterized. E...
Source: Journal of Chemical Physics - October 5, 2016 Category: Physics Authors: David Cappelletti, Stefano Falcinelli and Fernando Pirani Source Type: research
Communication: Thermal unimolecular decomposition of syn-CH3CHOO: A kinetic study
The thermal decomposition of syn-ethanal-oxide (syn-CH3CHOO) through vinyl hydrogen peroxide (VHP) leading to hydroxyl radical is characterized using a modification of the HEAT thermochemical protocol. Theisomerization step of syn-CH3CHOO to VHP via a 1,4 H-shift, which involves a moderate barrier of 72 kJ/mol, is found to be rate determining. A two-dimensional master equation approach, in combination with semi-classical transition state theory, is employed to calculate the time evolution of various species as well as to obtain phenomenological rate coefficients. This work suggests that, under boundary layer conditions in ...
Source: Journal of Chemical Physics - October 5, 2016 Category: Physics Authors: Thanh Lam Nguyen, Laura McCaslin, Michael C. McCarthy and John F. Stanton Source Type: research
Perspective: Kohn-Sham density functional theory descending a staircase
This article presents a perspective on Kohn-Sham density functional theory (KS-DFT) for electronic structure calculations in chemical physics. This theory is in widespread use for applications to both molecules and solids. We pay special attention to several aspects where there are both concerns and progress toward solutions. These include: 1. The treatment of open-shell and inherently multiconfigurational systems (the latter are often called multireference systems and are variously classified as having strongcorrelation, near-degeneracycorrelation, or high staticcorrelation; KS-DFT must treat these systems with broken-sym...
Source: Journal of Chemical Physics - October 5, 2016 Category: Physics Authors: Haoyu S. Yu, Shaohong L. Li and Donald G. Truhlar Source Type: research
Orientational distribution functions and order parameters in “de Vries”-type smectics: A simulation study
Simple smectic Aliquid crystal phases with different types of prescribed orientationaldistribution functions have been simulated and compared in order to study the possibility to distinguish between the Maier-Saupe type and cone-like orientational distributions using the popular method of Davidsonet al. [J. Phys. II5, 113 (1995)]. This method has been used to extract the orientationaldistribution functions from simulateddiffraction patterns, and the results have been compared with actualdistribution functions which have been prescribed during simulations. It has been shown that it is indeed possible to distinguish between ...
Source: Journal of Chemical Physics - October 4, 2016 Category: Physics Authors: Frank Jenz, Mikhail A. Osipov, Stefan Jagiella and Frank Giesselmann Source Type: research
The Cassie-Wenzel transition of fluids on nanostructured substrates: Macroscopic force balance versus microscopic density-functional theory
Classicaldensity functional theory is applied to investigate the validity of a phenomenological force-balance description of the stability of the Cassie state ofliquids on substrates with nanoscale corrugation. A bulkfree-energy functional of third order in local density is combined with a square-gradient term, describing the liquid-vaporinterface. The bulkfree energy is parameterized to reproduce theliquid density and the compressibility of water. The square-gradient term is adjusted to model the width of the water-vaporinterface. The substrate is modeled by an external potential, based upon the Lennard-Jonesinteractions....
Source: Journal of Chemical Physics - October 4, 2016 Category: Physics Authors: Nikita Tretyakov, Periklis Papadopoulos, Doris Vollmer, Hans-J ürgen Butt, Burkhard Dünweg and Kostas Ch. Daoulas Source Type: research
