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#### Surface free energy of platinum nanoparticles at zero pressure: A molecular dynamic study

, Article Solid State Communications ; Volume 150, Issue 5-6 , February , 2010 , Pages 254-257 ; 00381098 (ISSN) ; Abroshan, H ; Parsafar, G. A ; Sharif University of Technology
2010

Abstract

Metallic nanoparticles are interesting because of their use in catalysis and sensors. The surface energy of the FCC platinum nanoparticles are investigated via molecular dynamics simulation using Quantum Sutton-Chen (QSC) potential. We have calculated the Gibbs free energy for the FCC platinum bulk and also for its nanoparticle. All calculations have been carried out at zero pressure. We have used the thermodynamic integration method to obtain the Gibbs free energy. The total Gibbs free energy is taken as the sum of its central bulk and its surface free energy. We have calculated the free energy of a platinum nanoparticle as a function of temperature

#### Study of two dimensional anisotropic Ising models via a renormalization group approach

, Article Physica A: Statistical Mechanics and its Applications ; Volume 392, Issue 22 , 2013 , Pages 5604-5614 ; 03784371 (ISSN) ; Akbarzadeh, H ; Abroshan, H ; Ranjbar, S ; Fortunelli, A ; Parsafar, G ; Sharif University of Technology
2013

Abstract

A method is developed to calculate the critical line of two dimensional (2D) anisotropic Ising model including nearest-neighbor interactions. The method is based on the real-space renormalization group (RG) theory with increasing block sizes. The reduced temperatures, Ks (where K=J/kBT and J, kB, and T are the spin coupling interaction, the Boltzmann constant, and the absolute temperature, respectively), are calculated for different block sizes. By increasing the block size, the critical line for three types of lattice, namely: triangular, square, and honeycomb, is obtained and found to compare well with corresponding results reported by Onsager in the thermodynamic limit. Our results also...

#### Permutation entropy and detrend fluctuation analysis for the natural complexity of cardiac heart interbeat signals

, Article Physica A: Statistical Mechanics and its Applications ; Volume 392, Issue 14 , 2013 , Pages 3106-3112 ; 03784371 (ISSN) ; Rahmani, M ; Taherkhani, F ; Akbarzadeh, H ; Abroshan, H ; Sharif University of Technology
2013

Abstract

We compute fractal dimension and permutation entropy for healthy and people who have experienced heart failure. Our result shows that permutation entropy is a suitable approach as well as detrend fluctuation analysis (DFA). The result of DFA shows that the fractal dimensions for healthy and heart failure are different as well as the permutation entropy result. The fluctuation value for permutation entropy for an individual who has experienced heart failure is bigger than for a healthy person. There is some specific change in the interbeat signal of a person who has experienced heart failure, but there is not previous trend for a healthy person

#### Denaturation of Drew-Dickerson DNA in a high salt concentration medium: Molecular dynamics simulations

, Article Journal of Computational Chemistry ; Volume 32, Issue 16 , September , 2011 , Pages 3354-3361 ; 01928651 (ISSN) ; Parsafar, G. A ; Abroshan, H ; Akbarzadeh, H ; Sharif University of Technology
2011

Abstract

We have performed molecular dynamics simulation on B-DNA duplex (CGCGAATTGCGC) at different temperatures. The DNA was immerged in a salt-water medium with 1 M NaCl concentration to investigate salt effect on the denaturation process. At each temperature, configurational entropy is estimated using the covariance matrix of atom-positional fluctuations, from which the melting temperature (T m) was found to be 349 K. The calculated configuration entropy for different bases shows that the melting process involves more peeling (including fraying from the ends) conformations, and therefore the untwisting of the duplex and peeling states form the transition state of the denaturation process. There...

#### Calculation of melting temperature and transition curve for dickerson DNA dodecamer on the basis of configurational entropy, hydrogen bonding energy, and heat capacity: A molecular dynamics simulation study

, Article Journal of the Iranian Chemical Society ; Volume 8, Issue 3 , 2011 , Pages 708-716 ; 1735207X (ISSN) ; Parsafar, G. A ; Abroshan, H ; Akbarzade, H ; Sharif University of Technology
Abstract

A familiarity with denaturation process is highly significant in understanding the DNA replication, manipulation, and interactions involving DNA double helix stability. We have performed molecular dynamics simulation on B-DNA duplex (CGCGAATTGCGC) at different temperatures. At each temperature, configurational entropy was estimated using the covariance matrix of atom-positional fluctuations. By plotting the configuration entropy versus temperature, we calculated the melting temperature which was found to be 329.7 K. We also calculated the hydrogen bonding energy and heat capacity for the atoms participating in the hydrogen bonding between two strands of DNA. Moreover, their temperature...

#### Investigation of magnetic field effect on surface and finite-site free energy in one-dimensional Ising model of nanosystems

, Article Phase Transitions ; Volume 84, Issue 7 , Dec , 2011 , Pages 613-623 ; 01411594 (ISSN) ; Abroshan, H ; Akbarzadeh, H ; Parsafar, G ; Fortunelli, A ; Sharif University of Technology
2011

Abstract

We investigate a one-dimensional (1-D) Ising model for finite-site systems. The finite-site free energy and the surface free energy are calculated via the transfer matrix method. We show that, at high magnetic fields, the surface free energy has an asymptotic limit. The absolute surface energy increases when the value of f (the ratio of magnetic field to nearest-neighbor interactions) increases, and for f ≥10 approaches a constant value. For the values of f ≥0.2, the finite-site free energy also increases, but slowly. The thermodynamic limit in which physical properties approach the bulk value is also explored

#### Calculation of thermodynamic properties of Ni nanoclusters via selected equations of state based on molecular dynamics simulations

, Article Solid State Communications ; Volume 151, Issue 14-15 , 2011 , Pages 965-970 ; 00381098 (ISSN) ; Abroshan, H ; Taherkhani, F ; Parsafar, G. A ; Sharif University of Technology
2011

Abstract

We present an approach for constant-pressure molecular dynamics simulations. This approach is especially designed for finite systems, for which no periodic boundary condition applies. A molecular dynamics (MD) simulation for Ni nanoclusters is used to calculate their pressurevolumetemperature (pvT) data for the temperature range 200 K≤T≤400 K, and pressures up to 600 kbar. Isothermal sets of pvT data were generated by the simulation; each set was fitted by three equations of state (EoSs): Linear Isotherm Regularity-II (LIRII), BirchMurnaghan (BM), and EOS III. It is found that the MD data are satisfactorily reproduced by the EoSs with reasonable precision. Some features of the EoSs criteria,...

#### Size dependence and effect of potential parameters on properties of nano-cavities in liquid xenon using molecular dynamics simulation

, Article Chemical Physics ; Volume 381, Issue 1-3 , March , 2011 , Pages 44-48 ; 03010104 (ISSN) ; Abroshan, H ; Taherkhani, F ; Izanloo, C ; Parsafar, G. A ; Sharif University of Technology
2011

Abstract

We have investigated the size dependence of a nano-cavity properties produced in a Xe fluid using molecular dynamics simulations. We have created a nano-cavity of different sizes at 170 and 200 K (cavities diameters are within 1-10 nm). Liquid pressure, vapor pressure and surface tension of the nano-cavity for some given values of diameter are calculated. Within 1-10 nm cavity diameter, we have observed two opposite behavior for dependency of surface tension on the cavity diameter: for the range of 1-5 nm, it increases with the diameter, while, for the range of 5-10 nm remains constant. Also, the value of liquid pressure becomes less negative, when the size of cavity increases. Vapor...

#### On the existence of an analytic solution to the 1-D Ising model with nearest and next-nearest neighbor interactions in the presence of a magnetic field

, Article Phase Transitions ; Volume 84, Issue 1 , Dec , 2011 , Pages 77-84 ; 01411594 (ISSN) ; Daryaei, E ; Abroshan, H ; Akbarzadeh, H ; Parsafar, G ; Fortunelli, A ; Sharif University of Technology
2011

Abstract

To solve the controversy, regarding the existence of an analytic solution to the 1-D Ising model with nearest-neighbor (NN) and next-nearest-neighbor (NNN) interactions in the presence of a magnetic field, we apply the transfer matrix method to solve the 1-D Ising model in the presence of a magnetic field, taking both NN and NNN interactions into account. We show that it is possible to write a transfer matrix only if the number of sites is even. Even in such a case, it is impossible to diagonalize the transfer matrix in an analytic form. Therefore, we employ a numerical method to obtain the eigenvalues of the transfer matrix. Moreover, the heat capacity, magnetization, and magnetic...