We perform extensive molecular dynamics simulations to study the mass size distribution of a two-... more We perform extensive molecular dynamics simulations to study the mass size distribution of a two-dimensional fragmentation process. Our model consists of a large number of particles interacting through the Lennard–Jones potential. The fragmentation is induced by suddenly imposing a radial component on the particles' velocities, in order to mimic an explosion phenomenon. We then investigate the effect of the input energy on the resulting mass distribution of fragments.
We perform extensive molecular dynamics simulations to study the mass size distribution of a two-... more We perform extensive molecular dynamics simulations to study the mass size distribution of a two-dimensional fragmentation process. Our model consists of a large number of particles interacting through the Lennard–Jones potential. The fragmentation is induced by suddenly imposing a radial component on the particles' velocities, in order to mimic an explosion phenomenon. We then investigate the effect of the input energy on the resulting mass distribution of fragments.
Availability of highly reactive halogen ions at the surface of aerosols has tremendous implicatio... more Availability of highly reactive halogen ions at the surface of aerosols has tremendous implications for the atmospheric chemistry. Yet neither simulations, experiments, nor existing theories are able to provide a fully consistent description of the electrolyte-air interface. In this paper a new theory is proposed which allows us to explicitly calculate the ionic density profiles, the surface tension, and the electrostatic potential difference across the solution-air interface. Predictions of the theory are compared to experiments and are found to be in excellent agreement. The theory also sheds new light on one of the oldest puzzles of physical chemistry -- the Hofmeister effect.
The phase behavior of the lattice restricted primitive model (RPM) for ionic systems with additio... more The phase behavior of the lattice restricted primitive model (RPM) for ionic systems with additional short-range nearest neighbor (nn) repulsive interactions has been studied by grand canonical Monte Carlo simulations. We obtain a rich phase behavior as the nn strength is varied. In particular, the phase diagram is very similar to the continuum RPM model for high nn strength. Specifically, we have found both gas-liquid phase separation, with associated Ising critical point, and first-order liquid-solid transition. We discuss how the line of continuous order-disorder transitions present for the low nn strength changes into the continuum-space behavior as one increases the nn strength and compare our findings with recent theoretical results by Ciach and Stell [Phys. Rev. Lett. {\bf 91}, 060601 (2003)].
Following the suggestion in the Comment on our previous work by Åström, Linna, and Timonen [Phys.... more Following the suggestion in the Comment on our previous work by Åström, Linna, and Timonen [Phys. Rev. E 65, 048101 (2002)], we performed extensive molecular-dynamics simulations to confirm that our numerical results for the mass distribution of fragments after the ``explosion'' of thermalized samples are consistent with the scaling form n(m)~m-(alpha+1)f(m/M0), where f(m/M0) is a cutoff function, M0 is a
Physical review. E, Statistical, nonlinear, and soft matter physics, 2012
We introduce an implicit solvent Molecular Dynamics approach for calculating ionic fluxes through... more We introduce an implicit solvent Molecular Dynamics approach for calculating ionic fluxes through narrow nanopores and transmembrane channels. The method relies on a dual-control-volume grand-canonical molecular dynamics (DCV-GCMD) simulation and the analytical solution for the electrostatic potential inside a cylindrical nanopore recently obtained by Levin [Europhys. Lett. 76, 163 (2006)]. The theory is used to calculate the ionic fluxes through an artificial transmembrane channel which mimics the antibacterial gramicidin A channel. Both current-voltage and current-concentration relations are calculated under various experimental conditions. We show that our results are comparable to the characteristics associated to the gramicidin A pore, especially the existence of two binding sites inside the pore and the observed saturation in the current-concentration profiles.
Physical review. E, Statistical, nonlinear, and soft matter physics, 2001
A simple model is presented for the appearance of attraction between two like-charged polyions in... more A simple model is presented for the appearance of attraction between two like-charged polyions inside a polyelectrolyte solution. The polyions are modeled as rigid cylinders in a continuum dielectric solvent. The strong electrostatic interaction between the polyions and the counterions results in counterion condensation. If the two polyions are sufficiently close to each other their layers of condensed counterions can become correlated resulting in attraction between the macromolecules. To explore the counterion induced attraction we calculate the correlation functions for the condensed counterions. It is found that the correlations are of very short range. For the parameters specific to the double stranded DNA, the correlations and the attraction appear only when the surface-to-surface separation is less than 7 A.
Metodologia A metodologia a ser utilizada envolve a utilização de simulação computacional, atravé... more Metodologia A metodologia a ser utilizada envolve a utilização de simulação computacional, através da utilização do pacote ESPResSo (veja http://www. espresso. mpg. de). O pacote foi desenvolvido para realizar simulação computacional utilizando o ...
We investigate the explosive fragmentation process in two dimensions using molecular-dynamics sim... more We investigate the explosive fragmentation process in two dimensions using molecular-dynamics simulations. We show that the mass distribution of fragments follows a power law, with a scaling exponent that is strongly dependent on the macroscopic characteristics of the system prior to the explosion process. In particular, for thermalized initial configurations at low temperatures, we observe that the exponent is close to -1. We suggest that this result can be interpreted in terms of a multiplicative fracture process.
We perform extensive molecular dynamics simulations to study the mass size distribution of a two-... more We perform extensive molecular dynamics simulations to study the mass size distribution of a two-dimensional fragmentation process. Our model consists of a large number of particles interacting through the Lennard–Jones potential. The fragmentation is induced by suddenly imposing a radial component on the particles' velocities, in order to mimic an explosion phenomenon. We then investigate the effect of the input energy on the resulting mass distribution of fragments.
We perform extensive molecular dynamics simulations to study the mass size distribution of a two-... more We perform extensive molecular dynamics simulations to study the mass size distribution of a two-dimensional fragmentation process. Our model consists of a large number of particles interacting through the Lennard–Jones potential. The fragmentation is induced by suddenly imposing a radial component on the particles' velocities, in order to mimic an explosion phenomenon. We then investigate the effect of the input energy on the resulting mass distribution of fragments.
Availability of highly reactive halogen ions at the surface of aerosols has tremendous implicatio... more Availability of highly reactive halogen ions at the surface of aerosols has tremendous implications for the atmospheric chemistry. Yet neither simulations, experiments, nor existing theories are able to provide a fully consistent description of the electrolyte-air interface. In this paper a new theory is proposed which allows us to explicitly calculate the ionic density profiles, the surface tension, and the electrostatic potential difference across the solution-air interface. Predictions of the theory are compared to experiments and are found to be in excellent agreement. The theory also sheds new light on one of the oldest puzzles of physical chemistry -- the Hofmeister effect.
The phase behavior of the lattice restricted primitive model (RPM) for ionic systems with additio... more The phase behavior of the lattice restricted primitive model (RPM) for ionic systems with additional short-range nearest neighbor (nn) repulsive interactions has been studied by grand canonical Monte Carlo simulations. We obtain a rich phase behavior as the nn strength is varied. In particular, the phase diagram is very similar to the continuum RPM model for high nn strength. Specifically, we have found both gas-liquid phase separation, with associated Ising critical point, and first-order liquid-solid transition. We discuss how the line of continuous order-disorder transitions present for the low nn strength changes into the continuum-space behavior as one increases the nn strength and compare our findings with recent theoretical results by Ciach and Stell [Phys. Rev. Lett. {\bf 91}, 060601 (2003)].
Following the suggestion in the Comment on our previous work by Åström, Linna, and Timonen [Phys.... more Following the suggestion in the Comment on our previous work by Åström, Linna, and Timonen [Phys. Rev. E 65, 048101 (2002)], we performed extensive molecular-dynamics simulations to confirm that our numerical results for the mass distribution of fragments after the ``explosion'' of thermalized samples are consistent with the scaling form n(m)~m-(alpha+1)f(m/M0), where f(m/M0) is a cutoff function, M0 is a
Physical review. E, Statistical, nonlinear, and soft matter physics, 2012
We introduce an implicit solvent Molecular Dynamics approach for calculating ionic fluxes through... more We introduce an implicit solvent Molecular Dynamics approach for calculating ionic fluxes through narrow nanopores and transmembrane channels. The method relies on a dual-control-volume grand-canonical molecular dynamics (DCV-GCMD) simulation and the analytical solution for the electrostatic potential inside a cylindrical nanopore recently obtained by Levin [Europhys. Lett. 76, 163 (2006)]. The theory is used to calculate the ionic fluxes through an artificial transmembrane channel which mimics the antibacterial gramicidin A channel. Both current-voltage and current-concentration relations are calculated under various experimental conditions. We show that our results are comparable to the characteristics associated to the gramicidin A pore, especially the existence of two binding sites inside the pore and the observed saturation in the current-concentration profiles.
Physical review. E, Statistical, nonlinear, and soft matter physics, 2001
A simple model is presented for the appearance of attraction between two like-charged polyions in... more A simple model is presented for the appearance of attraction between two like-charged polyions inside a polyelectrolyte solution. The polyions are modeled as rigid cylinders in a continuum dielectric solvent. The strong electrostatic interaction between the polyions and the counterions results in counterion condensation. If the two polyions are sufficiently close to each other their layers of condensed counterions can become correlated resulting in attraction between the macromolecules. To explore the counterion induced attraction we calculate the correlation functions for the condensed counterions. It is found that the correlations are of very short range. For the parameters specific to the double stranded DNA, the correlations and the attraction appear only when the surface-to-surface separation is less than 7 A.
Metodologia A metodologia a ser utilizada envolve a utilização de simulação computacional, atravé... more Metodologia A metodologia a ser utilizada envolve a utilização de simulação computacional, através da utilização do pacote ESPResSo (veja http://www. espresso. mpg. de). O pacote foi desenvolvido para realizar simulação computacional utilizando o ...
We investigate the explosive fragmentation process in two dimensions using molecular-dynamics sim... more We investigate the explosive fragmentation process in two dimensions using molecular-dynamics simulations. We show that the mass distribution of fragments follows a power law, with a scaling exponent that is strongly dependent on the macroscopic characteristics of the system prior to the explosion process. In particular, for thermalized initial configurations at low temperatures, we observe that the exponent is close to -1. We suggest that this result can be interpreted in terms of a multiplicative fracture process.
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Papers by Alexandre Diehl