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Communications in Theoretical Physics 2014年第8期61卷 283-289页

作者： r.khordad H.Bahramiyan Department of Physics College of Sciences Yasouj University yasouj 75914-353 iran

In the present work, we have studied electronic and optical properties of a lens-shaped quantum dot under an external magnetic field. For this goal, we have calculated the energy levels and wave functions using the finite element method(FEM) for different values of magnetic field. We have also studied effect of magnetic field on second harmonic generation(SHG) and third-harmonic generation(THG) in the lens-shaped quantum dot. In this regard, we have obtained an analytic expression for the SHG and THG by a compact density matrix approach and an iterative procedure. According to the obtained results, it is found that the presence of the magnetic field affects the symmetry of the system. The SHG and THG are decreased with increasing the magnetic field. The magnetic field has a great influence on the energy levels, wave functions, the SHG and THG in a lens shaped quantum dot.

关键词： quantum dot optical properties harmonic generations magnetic field

Application of Tietz Potential to Study Singlet-Triplet Transition of a Two-Electron Quantum Dot

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Communications in Theoretical Physics 2014年第7期61卷 77-80页

作者： r.khordad B.Mirhosseini Department of Physics College of Sciences Yasouj University

In this paper, we have studied electronic properties of a two-electron quantum dot using Tietz confining potential in the presence of an external magnetic field. In this regard, we have applied diagonalization procedure of Hamilonian matrix. We have calculated singlet-triplet ground state transitions as a function of the magnetic field. The obtained results show that the dot size of the Tietz potential has an important role in the ground state transition. The singlet-triplet transition of the ground state shifts towards lower magnetic field when the quantum size increases. Our results yield much less transitions than that of previous results [r.G. Nazmitdinov, N.S. Simonovic, and M.J. rost, ***. B 65(2002) 155307].

关键词： quantum dot singlet-triplet transition Tietz potential

Strain Effect on the Absorption Threshold Energy of Silicon Circular Nanowires

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Communications in Theoretical Physics 2016年第1期65卷 87-91页

作者： r.khordad H.Bahramiyan Department of Physics College of SciencesYasouj University

In this work,the influence of strain on threshold energy of absorption in Silicon circular nanowires is *** this purpose,we first have used the density functional theory(DFT) to calculate the electron and hole effective ***,we have obtained absorption threshold energy with two different procedures,DFT and effective mass approximation(EMA).We have also obtained the band structures of Si nanowires both DFT and *** results show that:i) the expansive strain increases the hole effective mass while compressive strain increases the electron effective mass,ii) the electron and hole effective masses reduce with decreasing the wire size,iii) the absorption threshold energy decreases by increasing strain for compressive and tensile strain and its behavior as a function of strain is approximately parabolic,iv) the absorption threshold energy(for all sizes) obtained using EMA is greater than the DFT results.

关键词：应变效应吸收循环硅纳米线阈值能量有效质量圆形密度泛函理论能量阈值

An analytical study of vibration in functionally graded piezoelectric nanoplates: nonlocal strain gradient theory

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Applied Mathematics and Mechanics(English Edition) 2019年第12期40卷 1723-1740页

作者： Z.SHArIFI r.khordad A.GHArAATI G.FOrOZANI Department of Physics Payame Noor UniversityTehran 19395-3697Iran department of physics college of scienceyasouj universityyasouj 75914-353iran

In this paper,we analytically study vibration of functionally graded piezoelectric(FGP)nanoplates based on the nonlocal strain gradient *** top and bottom surfaces of the nanoplate are made of PZT-5H and PZT-4,*** employ Hamilton’s principle and derive the governing differential ***,we use Navier’s solution to obtain the natural frequencies of the FGP *** the first step,we compare our results with the obtained results for the piezoelectric nanoplates in the previous *** the second step,we neglect the piezoelectric effect and compare our results with those obtained for the functionally graded(FG)***,the effects of the FG power index,the nonlocal parameter,the aspect ratio,and the lengthto-thickness ratio,and the nanoplate shape on natural frequencies are investigated.

关键词： nonlocal strain gradient nanoplate functionally graded piezoelectric(FGP)

Simultaneous Effects of Impurity and Electric Field on Entropy Behavior in Double Cone-Like Quantum Dot

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Communications in Theoretical Physics 2018年第1期69卷 95-100页

作者： r.khordad H.r.rastegar Sedehi H.Bahramiyan Department of Physics College of Sciences Yasouj University Department of Physics Jahrom University Department of Optics and Laser Engineering Marvdasht Branch Islamic Azad University

In this work, the simultaneous effects of electric field and impurity on the non-extensive entropy of a GaAs/Ga;In;As double cone-like quantum dot that is grown on a Ga As wet layer are studied. The system is under an external electric field directed along the-x direction. First, we have solved the Schr¨odinger equation using the finite element method. Then, we have used the Tsallis formalism and calculated the entropy of the system for different temperatures, electric fields and impurity locations. It is found that the entropy decreases with increasing the electric field and temperature. Since the electric field directed along the-x direction, the entropy reduces when the impurity moves toward the left hand side.

关键词： entropy double quantum dot electric field

Quantum Wire with Triangle Cross Section:Optical Properties

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Communications in Theoretical Physics 2012年第6期57卷 1076-1080页

作者： r.khordad S.Tafaroji r.Katebi A.Ghanbari Department of Physics College of SciencesYasouj UniversityYasouj 75914-353Iran

In the present work,the optical properties of a GaAs quantum wire with equilateral triangle cross section are *** this purpose,we use analytical expressions for optical properties obtained by the compact-density matrix ***,we investigate the intersubband optical absorption coefficients and refractive index changes as a function of the triangle side(L) and the incident optical intensity(I).According to the obtained results,it is found that:(i) The total refractive index changes increase and shift towards lower energies when the triangle side increases.(ii) The total absorption coefficient decreases as the triangle side ***,the resonance peak shifts towards lower energies by increasing the triangle side.

关键词： quantum wire optical properties

Inhomogeneous 2D Lennard-Jones Fluid: Theory and Computer Simulation

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Communications in Theoretical Physics 2012年第11期58卷 759-764页

作者： r. khordad Department of Physics College of SciencesYasouj University

In this work, thermodynamical properties of a two-dimensional (2D) Lennard-Jones (LJ) fluid are studied. Here, to increase the accuracy of our theoretical calculations, the correlation functions in three-particle level (triplet) are applied. To obtain the triplet correlation functions, the Attard's source particle method is extended to 2D systems. In the Attard's procedure, the inhomogeneous Ornstein-Zernike (OZ) equation is solved using the Treizenberg-Zwanzwig (TZ) expression and a closure relation like the hypernetted-chain (HNC) approximation. In the present work, we also have performed the Monte Carlo (MC) simulation. The theoretical results are in fairly agreement with the MC simulation. Also, our results show that the approach proposed here is suitable to study the 2D LJ fluid.

关键词：计算机模拟流体理论二维非均匀 MC模拟热力学性质相关函数三重相关

Effect of Magnetic Field on Internal Energy and Entropy of a Parabolic Cylindrical Quantum Dot

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Communications in Theoretical Physics 2013年第5期59卷 655-660页

作者： r. khordad M.A. Sadeghzadeh A. Mohamadian Jahan-abad Department of Physics College of SciencesYasouj University Department of Physics College of SciencesYazd University

In the present work, the entropy and internal energy of a GaAs cylindrical quantum dot in the presence of an applied magnetic field is studied. For this purpose, the Tsallis formalism is applied to obtain internal energy and entropy. It is found that entropy and internal energy are continuous function and they are zero at special temperatures. Entropy maximum increases with increasing dot radius. Internal energy increases by increasing magnetic field.

关键词： quantum dot entropy magnetic field internal energy