Department of Condensed Matter Physics (2016 - Present)
Statistical Physics
Physics, Shiraz University, Shiraz, Iran
Statistical Physics
Physics, Shiraz University, Shiraz, Iran
Physics
Physics, Sharif University of Technology, Tehran, Iran
Malihe Ghodrat has completed her BSc in Physics at Sharif University of Technology and earned her PhD in Condensed Matter Physics from Shiraz University in 2011. In her PhD dissertation, she has developed an event-driven molecular dynamic model of relativistic gaseous systems, focusing on thermostatistical properties, transport coefficients and propagation of fluctuations. She then moved to Institute for Research in Fundamental Sciences (IPM) in Tehran as a postdoctoral researcher, where she has been studying charge disorder dielectric surfaces embedded in ionic fluids and the type of interactions that are involved due to the coupling between electrostatic interactions and surface charge randomness. She is now conducting a research group in Statistical and Soft Matter Physics at Tarbiat Modares University, focusing on statistical properties of self propelled particles using Brownian dynamics simulation.
Transport coefficients are of crucial importance in theoretical as well as experimental studies. Despite substantial research on classical hard sphere or disk gases in low-and high-density regimes, a thorough investigation of transport coefficients for massive relativistic systems is missing in the literature. In this work a fully relativistic molecular dynamics simulation is employed to numerically obtain the transport coefficients of a hard sphere relativistic gas based on Helfand-Einstein expressions. The numerical data are then used to check the accuracy of Chapmann-Enskog (CE) predictions in a wide range of temperature. The results indicate that while simulation data in low-temperature regime agrees very well with theoretical predictio
We investigate the effective interaction between two randomly charged but otherwise net-neutral, planar dielectric slabs immersed in an asymmetric Coulomb fluid containing a mixture of mobile monovalent and multivalent ions. The presence of charge disorder on the apposed bounding surfaces of the slabs leads to substantial qualitative changes in the way they interact, as compared with the standard picture provided by the van der Waals and image-induced, ion-depletion interactions. While, the latter predict purely attractive interactions between strictly neutral slabs, we show that the combined effects from surface charge disorder, image depletion, Debye (or salt) screening, and also, in particular, their coupling with multivalent ions, give
We study the effective interaction mediated by strongly coupled Coulomb fluids between dielectric surfaces carrying quenched, random monopolar charges with equal mean and variance, both when the Coulomb fluid consists only of mobile multivalent counterions and when it consists of an asymmetric ionic mixture containing multivalent and monovalent (salt) ions in equilibrium with an aqueous bulk reservoir. We analyze the consequences that follow from the interplay between surface charge disorder, dielectric and salt image effects, and the strong electrostatic coupling that results from multivalent counterions on the distribution of these ions and the effective interaction pressure they mediate between the surfaces. In a dielectrically homogeneo
We study the distribution of multivalent counterions next to a dielectric slab, bearing a quenched, random distribution of charges on one of its solution interfaces, with a given mean and variance, both in the absence and in the presence of a bathing monovalent salt solution. We use the previously derived approach based on the dressed multivalent-ion theory that combines aspects of the strong and weak coupling of multivalent and monovalent ions in a single framework. The presence of quenched charge disorder on the charged surface of the dielectric slab is shown to substantially increase the density of multivalent counterions in its vicinity. In the counterion-only model (with no monovalent salt ions), the surface disorder generates an addit
Recently, a morphological transition in the velocity distribution of a relativistic gas has been pointed out which shows hallmarks of a critical phenomenon. Here, we provide a general framework which allows for a thermodynamic approach to such a critical phenomenon. We therefore construct a thermodynamic potential which upon expansion leads to Landau-like (mean-field) theory of phase transition. We are therefore able to calculate critical exponents and explain the spontaneous emergence of “order parameter” as a result of relativistic constraints. Numerical solutions which confirm our thermodynamic approach are also provided. Our approach provides a general understanding of such a transition as well as leading to some new results. Finall
Relativistic transport phenomena are important from both a theoretical and practical point of view. Accordingly, hydrodynamics of relativistic gas has been extensively studied theoretically. Here we introduce a three-dimensional canonical model of hard-sphere relativistic gas which allows us to impose appropriate temperature gradient along a given direction maintaining the system in a nonequilibrium steady state. We use such a numerical laboratory to study the appropriateness of the so-called first order (Chapman-Enskog) relativistic hydrodynamics by calculating various transport coefficients. Our numerical results are consistent with predictions of such a theory for a wide range of temperatures. Our results are somewhat surprising since su
The introduction of models to simulate dynamics of relativistic gaseous systems is among the latest efforts made in the recent decades to investigate the relativistic generalizations of statistical thermodynamics. Relativistic thermodynamics was born in the early 20th century to investigate the consequences of Einstien’s special relativity on thermodynamic systems. A simple and important question is the Lorentz transformation property of temperature. Other questions are related to relativistic generalization of equilibrium statistical mechanics. For example, Maxwell-Boltzmann (MB) distribution, the corner stone of classical statistical mechanics, permits velocities greater than the speed of light, v> c, in direct conflict with a basic ass
Studying special relativistic generalizations of classical thermodynamic systems have recently attracted much attention despite its long and controversial history. Here, we propose a relativistic model of a realistic dilute gas which can easily be studied using standard molecular dynamics simulations. We briefly outline some of its thermostatistical properties which help resolve controversial issues in relativistic thermodynamics. In particular, we find that J?ttner function is the correct generalization of Maxwell–Boltzmann velocity distribution. We also conclude that relativistic temperature is best understood as a rest-frame-property, invariant under various relativistic transformations, i.e. Lorentz transformation and time reparametri
Classical statistical thermodynamics is one of the oldest, most well‐established physical theories and its basis and results have not been challenged within its domain since the time of Boltzmann. Special relativity, however, introduces some constraints as well as ambiguities into such a theory. For example, the cornerstone of classical statistical mechanics, the Maxwell‐Boltzmann (MB) distribution does not respect the maximal velocity of light, the cornerstone of special relativity. Additionally, the Lorentz transformation of temperature, i.e. how a moving body’s temperature compares to its rest frame value, has long caused controversies. Special relativity also introduces a new concept of proper time, which could potentially affect
In this paper we consider the effect of different time parametrizations on the stationary velocity distribution function for a relativistic gas. We clarify the distinction between two such distributions, namely, the J?ttner and the Modified J?ttner distributions. Using a recently proposed model of a relativistic gas, we show that the obtained results for the proper-time averaging does not lead to the Modified J?ttner distribution (as recently conjectured), but introduces a Lorentz factor γ (v)(ie, energy) to the well-known J?ttner function which results from observer-time averaging. These two modifications (ie, Modified J?ttner function or J?ttner divided by energy) are identical in the rest frame; however, their distinction comes to light
In this paper we study a fully relativistic model of a two-dimensional hard-disk gas. This model avoids the general problems associated with relativistic particle collisions and is therefore an ideal system to study relativistic effects in statistical thermodynamics. We study this model using molecular-dynamics simulation, concentrating on the velocity distribution functions. We obtain results for x and y components of velocity in the rest frame (Γ) as well as the moving frame (Γ′). Our results confirm that J?ttner distribution is the correct generalization of Maxwell-Boltzmann distribution. We obtain the same “temperature” parameter β for both frames consistent with a recent study of a limited one-dimensional model. We also addres
We study the distribution of multivalent counterions next to a dielectric slab, bearing a quenched, random distribution of charges on one of its solution interfaces, with a given mean and variance, both in the absence and in the presence of a bathing monovalent salt solution. We use the previously derived approach based on the dressed multivalent-ion theory that combines aspects of the strong and weak coupling of multivalent and monovalent ions in a single framework. The presence of quenched charge disorder on the charged surface of the dielectric slab is shown to substantially increase the density of multivalent counterions in its vicinity. In the counterion-only model (with no monovalent salt ions), the surface disorder generates an addit
no record found