Optimized resonating valence bond state in square lattice: correlations & excitations
Z
Nourbakhsh
author
F
Shahbazi
author
SA
Jafari
author
text
article
2019
per
We consider RVB state as a variational estimate for the ground state of Heisenberg antiferromagnet in square lattice. We present numerical calculation of energy, spin-spin correlation function and spin excitation spectrum. We show, that the quantum flactuations reduce of magnetization respect to Neel order. Our results are in good agreement with other methods such as spin-wave calculation and series expansions.
Iranian Journal of Physics Research
https://www.psi.ir/physics_society_iran_1_home
1682-6957
9
v.
2
no.
2019
131
136
http://ijpr.iut.ac.ir/article_809_e5d6bdc5b7b973667323b889e2832067.pdf
Band structure of fcc-C60 solid state crystal study
S
Javanbakht
دانشگاه اصفهان
author
S
Jalali Asadabadi
author
text
article
2019
per
We studied the architecture of the C60 cluster to drive its atomic positions which can be seen at room temperature. We then used the obtained carbon positions as a basis set for the fcc structure to construct the fcc-C60 compound. Self consistent calculations were performed based on the density functional theory (DFT) utilizing the accurate WIEN2K code to solve the single-particle Kohen-Sham equation within the augmented plane waves plus local orbital (APW+lo) method. The cohesive energy has been found to be 1.537 eV for the fcc-C60 . The calculated small cohesive energy that results from the weak Van der Waals-London interactions among a C60 cluster with its nearest neighbors is in good agreement with experiment. The electron densities of states (DOSs) were calculated for a C60 macromolecule as well as the fcc-C60 compound and the results were compared with each other. The band gap from DOS calculations has been found to be 0.7 eV. Band structures were also calculated within the generalized gradient approximation (GGA). The band structure calculation results in 1.04 eV for the direct band gap. Two kinds of σ and π bonds were determined in the band structure. Our results are in good agreement with experiment and pseudopotential calculations.
Iranian Journal of Physics Research
https://www.psi.ir/physics_society_iran_1_home
1682-6957
9
v.
2
no.
2019
137
147
http://ijpr.iut.ac.ir/article_810_9b59bb4bbefa1b695661d043bc52307f.pdf
Generalization of the Jarzynski equation for a system with variable temperature
S
Zare
author
Z
Ebadi
author
B
Mirza
author
text
article
2019
per
Recently the Jarzynski equation have been under many investigations. In this equation a relation between the average exponential of the work done on a system under non-equilibrium condition and equilibrium free energy differences is established. In different papers the equation has already been extended to different conditions. In this paper we will extend it to a situation that a system is driven away from equilibrium by work performed on it but with a non-constant temperature. Then this generalized equation will be applied to one-dimensional classical and quantum harmonic oscillators.
Iranian Journal of Physics Research
https://www.psi.ir/physics_society_iran_1_home
1682-6957
9
v.
2
no.
2019
149
155
http://ijpr.iut.ac.ir/article_811_89195f5596e49fdffb7e0da15f7ca9ab.pdf
Two-state approximation applied to hydrogen formation by proton impact on positronium
E
Ghanbari Adivi
author
text
article
2019
per
Although there is no experimental data available for antihydrogen formation following antiprotons impact on positroium atoms, as a charge transfer reaction, at incident energies which are suitable for antimatter high-precision spectroscopic studies, measurements were carried out for its charge-conjugate reaction i. e. hydrogen formation, by protons impact on positronium. In this study, a two-state approximation method is applied to charge exchange process in proton-positronium collision system. The nonorthogonality of initial and final states and its effects on the angular distribution of the differential cross sections is taken into account by using this method. The state-to-state differential cross sections are reported for transition from ground state of positronium into the ground and a few lowest excited states of the formed hydrogen. Integrated cross sections are presented as well.
Iranian Journal of Physics Research
https://www.psi.ir/physics_society_iran_1_home
1682-6957
9
v.
2
no.
2019
157
164
http://ijpr.iut.ac.ir/article_812_f526769c411983276b7ab65d7156c105.pdf
Penguin decays in b quark
H
Mehrban
دانشگاه سمنان
author
text
article
2019
per
In this research, we are going to study the QCD penguin structure and calculate the second order approximation. The amplitude of decays related to QCD penguin in the quark model up to the first and second orders were calculated. We calculated the amplitude of QCD penguin on lowest order of αs for the first order of the decay processes b→qkg→qkqiqj and for the second order of the decay processes b→qkqiqj→ qkqiqjg→ qkqiqj(qoqp < /sub>). We calculated the decay rates of the first and second order of QCD penguin for various b quark decays. We consider that, the second order of QCD penguin of b quark decays to be much smaller than the first order. We calculated the branching ratios of b quark- b antiquark decays and assuming that we can ignore the second order of QCD penguin.
Iranian Journal of Physics Research
https://www.psi.ir/physics_society_iran_1_home
1682-6957
9
v.
2
no.
2019
165
176
http://ijpr.iut.ac.ir/article_813_1e78a4fb2f05f25f5ac3118d9526519f.pdf
Prediction of fission barrier height for induced fission reactions with 16O at several energies
S
Soheyli
author
F
Alizadeh
دانشگاه بوعلیسینا همدان
author
text
article
2019
per
We have calculated the fission barrier height for 16O+208Pb, 16O+209Bi, 16O+232Th, 16O+238U and 16O+248Cm systems in energy range between 90 MeV to 215 MeV. This method is based on the experimental data for angular anisotropies of fission fragments. In present work, we have used the transition state model (STM) for two different cases: the first case is without neutron emission correction and the second case is with neutron emission correction. In this paper, we have predicted the fission barrier for the two super heavy nuclei that were not reported previously with experimental methods.
Iranian Journal of Physics Research
https://www.psi.ir/physics_society_iran_1_home
1682-6957
9
v.
2
no.
2019
177
183
http://ijpr.iut.ac.ir/article_814_bdb84b2ea465261f91c349d265fb272e.pdf
Analyzing of DNA behavior in passing through micro-structures based on the Fokker-Planck equation and the entropic barrier model
N
Maleki-Jirsaraei
author
A
Fatemi
author
MN
Sarbolouki
author
SH
Rouhani
author
text
article
2019
per
We considered the motion of DNA molecules through a hexagonal array under uniform electric fields as a Fokker-Planck process which is affected by the entropic barriers and we have simulated this motion by computer. We solved the Fokker-Planck equation with numerical simulation of the Brownian dynamics by the Euler method. For different DNA molecules, under different physical conditions, the mean value of velocity, variance, and < x2 > have been calculated, and the results have been compared with the Phase Diagram of our previous results. In the light of this comparison we could find the physics of the DNA behavior in different regimes. It is observed that in regime-1 (small DNA molecules under weak Electric force) we have a pure diffusion process, in regime-3 (large DNA molecules under high Electric field) the entropic barrier model is the dominated physics, and in regime-2 (medium DNA molecules under medium and relative high Electric fields), which is a more complicated regime we have a drifted diffusion phenomenon.
Iranian Journal of Physics Research
https://www.psi.ir/physics_society_iran_1_home
1682-6957
9
v.
2
no.
2019
185
193
http://ijpr.iut.ac.ir/article_815_2b9d0ce8637468e43262caff6e779176.pdf
Magneto-optic properties and optical parameter of thin MnCo films
E
Attaran Kakhki
author
M
Adelifard
author
text
article
2019
per
Having precise hysterics loop of thin ferroelectric and ferromagnetic layers for optical switching and optical storages are important. A hysterieses loop can be achieved from a phenomenon call the magneto-optic effect. The magneto-optic effect is the rotation of a linear polarized electromagnetic wave propagated through a ferromagnetic medium. When light is transmitted through a layer of magnetic material the result is called the Faraday effects and in the reflection mode Kerr effect. In the present work we prepared a thin layer of MnxCo3-xO4 (0≤ x ≤ 1) and a binary form of MnO/Co3O4 by the spray pyrolysis method. The films have been characterized by a special set up of magneto-optic hysterics loop plotter containing a polarized He- Ne laser beam and a special electronic circuit. Faraday rotation were measured for these films by hysterics loop plotter and their optical properties were also obtained by spatial software designed for this purpose according to Swane Poel theoretical method. The measurements show that the samples at diluted Mn study has are ferromagnetic and the magneto-optic rotation show a good enhance respect to the single Co layers. Also, the study has shown that the MnCo oxide layer have two different energy gaps and by increasing of Mn this energy decreases and fall to 0.13 eV.
Iranian Journal of Physics Research
https://www.psi.ir/physics_society_iran_1_home
1682-6957
9
v.
2
no.
2019
195
202
http://ijpr.iut.ac.ir/article_816_4d24dab61b2e897f69157f3e2bb6915c.pdf
Multiplicity distribution of charged particles in e+ eâ annihilation in 54-57 GeV centre of mass energy and KNO scaling
A
Ghasempoor Nashli
author
A
Sepehri
author
T
Gaffary
author
ME
Zomorrodian
author
text
article
2019
per
In this paper, we investigate the multiplicity of charged particles in e+ e– annihilation by using different models. To achieve this we first fit the multiplicity distribution of charged particles in the energy range of 54-57 GeV by using both the Poisson distribution and KNO scaling, then we compare these results with multiplicity distribution at the lower energies. This comparison shows that our results are more compatible with KNO scaling in this energy range. Also we fit the multiplicity distribution of our data, together with the other data up to 206 GeV, to Fermi model, the pp data model and the model obtained from perturbative QCD. The coefficients obtained by these methods are consistent with those obtained at lower energies.
Iranian Journal of Physics Research
https://www.psi.ir/physics_society_iran_1_home
1682-6957
9
v.
2
no.
2019
203
207
http://ijpr.iut.ac.ir/article_817_9a1078c7330c364c7e09855dc54a8a6f.pdf
Effects of hyperfine interactions on masses of N and Î baryons
H
Hassanabadi
author
S
Zarrinkamar
author
AA
Rajabi
author
text
article
2019
per
Presenting a model for theoretical study of baryon masses, either in relativistic or nonrelativistic area, has always been of great importance and several suggestions have been proposed. On the other hand, taking into account the effects of hyperfine interactions leads to interesting results. In the present work, we first introduce the hyperfine interaction and the quark potential corresponding to the isospin interaction. We then obtain the wavefunctions as well as the corresponding eigenvalues. The obtained results for the spectrum of baryons show a good agreement with experimental results.
Iranian Journal of Physics Research
https://www.psi.ir/physics_society_iran_1_home
1682-6957
9
v.
2
no.
2019
209
213
http://ijpr.iut.ac.ir/article_818_bbd432537d6573e77471553acfa92b1b.pdf
Compton scattering as a probe for materials investigation
S
Mohammadi
author
text
article
2019
per
This article investigates into the feasibility of using gamma radiation Compton backscatter spectra as a means of material characterization, with the view to developing a portable, hand held probe for investigative purposes such as searching for illicit substances hidden in wall or car door cavities.
Iranian Journal of Physics Research
https://www.psi.ir/physics_society_iran_1_home
1682-6957
9
v.
2
no.
2019
215
215
http://ijpr.iut.ac.ir/article_819_a9180ff625d9d8cad9bd6a4156be660d.pdf
Calculating charge radius for proton with hyper central interacting color potential
H
Tayer
author
AA
Rajabi
author
text
article
2019
per
An improved M.I.T. bag model with hyper central interaction is used to calculate the charge radius for proton containing u and d quarks. We present a theoretical approach to the internal structure of three-body hyper central interacting quarks in a proton, in which we take proton as a bag. We discuss a few of results obtained using a six-dimension potential, which is attractive for small separation, originating from the color charge of hyper color term. We calculate the relativistic wave function for quarks in a scalar-vector hyper central potential, analytically. Finally, vanishing the normal component of vector current at the surface of the proton bag as a boundary condition equivalent to confinement. The calculated charge radius for proton is better than in the uncorrected versions of the model.
Iranian Journal of Physics Research
https://www.psi.ir/physics_society_iran_1_home
1682-6957
9
v.
2
no.
2019
216
216
http://ijpr.iut.ac.ir/article_820_40d8799f9fd7da0afab5f79f2b6988ef.pdf