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Electron energy spectrum of the spherical GaAs/AlxGa1-xAs quantum dot with several impurities on the surface 表面有杂质的球形GaAs/AlxGa1-xAs量子点的电子能谱
IF 0.6 4区 物理与天体物理 Q4 PHYSICS, CONDENSED MATTER Pub Date : 2023-05-25 DOI: 10.5488/CMP.26.23704
R. Leshko, I. V. Bilynskyi, O. V. Leshko, V. B. Hols'kyi
The model of a spherical quantum dot with several donor impurities on its surface is suggested. The electron energy spectra are studied as a function of the quantum dot radius and the number of impurities. Several cases of the location of impurities on the quantum dot surface are considered. The plane wave functions method has been applied to calculate the electron energy spectrum. The splitting of electron energy levels is analyzed in the cases of different number of impurities. It is shown that the electron energy splitting depends on both the number of impurities on the surface and on their location. The electron binding energy is defined too.
提出了球面量子点表面有几个给体杂质的模型。研究了电子能谱与量子点半径和杂质数的关系。考虑了杂质在量子点表面位置的几种情况。应用平面波函数法计算了电子能谱。分析了不同杂质数量情况下电子能级的分裂。结果表明,电子能量分裂与表面杂质的数量和位置有关。也定义了电子结合能。
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引用次数: 0
Computational study of structural, elastic, electronic, phonon dispersion relation and thermodynamic properties of orthorhombic CaZrS3 for optoelectronic applications 光电用正交型CaZrS3的结构、弹性、电子、声子色散关系及热力学性质的计算研究
IF 0.6 4区 物理与天体物理 Q4 PHYSICS, CONDENSED MATTER Pub Date : 2023-05-25 DOI: 10.5488/CMP.26.23701
M. Kassa, N. Debelo, M. Woldemariam
Chalcogenide perovskites offer superior thermal and aqueous stability as well as a benign elemental composition compared to organic halide perovskites for optoelectronic applications. In this study, the structural, electrical, elastic, phonon dispersion, and thermodynamic features of the orthorhombic phase of chalcogenide perovskite CaZrS3 (space group Pnma) were examined by first principles calculations utilizing the plane wave pseudopotentials (PW-PPs) in generalized gradient approximations (GGA). The ground state properties such as lattice parameters, unit cell volume, bulk modulus, and its derivative were calculated and are in a good agreement with existing findings. The mechanical properties such as bulk modulus, shear modulus, Young's modulus and elastic anisotropy were calculated from the obtained elastic constants. The ratio of bulk modulus to shear modulus confirms that the orthorhombic phase of CaZrS3 is a ductile material. The absence of negative frequencies in phonon dispersion curve and the phonon density of states give an indication that the structure is dynamically stable. Finally, thermodynamic parameters such as free energy, entropy, and heat capacity were calculated with variation in temperature. The estimated findings follow the same pattern as previous efforts.
与光电应用的有机卤化物钙钛矿相比,硫系钙钛矿具有优越的热稳定性和水稳定性以及良好的元素组成。在本研究中,利用广义梯度近似(GGA)中的平面波赝势(PW-PPs),利用第一性原理计算研究了硫系钙钛矿CaZrS3(空间群Pnma)正交相的结构、电学、弹性、声子色散和热力学特征。计算了基态性质,如晶格参数、单元胞体积、体积模量及其导数,并与现有研究结果相吻合。根据得到的弹性常数计算了材料的体模量、剪切模量、杨氏模量和弹性各向异性等力学性能。体积模量与剪切模量的比值证实了CaZrS3的正交相是一种延性材料。声子色散曲线中不存在负频率和声子态密度表明该结构是动态稳定的。最后,计算了随温度变化的自由能、熵和热容等热力学参数。估计的结果与之前的努力遵循相同的模式。
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引用次数: 0
Electronic structure and X-ray magnetic circular dichroism in the MAX phases T2AlC (T = Ti and Cr) from first principles 从第一性原理研究T2AlC (T = Ti和Cr) MAX相的电子结构和x射线磁圆二色性
IF 0.6 4区 物理与天体物理 Q4 PHYSICS, CONDENSED MATTER Pub Date : 2023-05-25 DOI: 10.5488/CMP.26.23706
L. Bekenov, S. V. Moklyak, B. F. Zhuravlev, Y. Kucherenko, V. Antonov
We study the electronic and magnetic properties of T2AlC (T = Ti and Cr) compounds in the density-functional theory using the generalized gradient approximation (GGA) with consideration of strong Coulomb correlations (GGA+U) in the framework of the fully relativistic spin-polarized Dirac linear muffin-tin orbital (LMTO) band-structure method. The X-ray absorption spectra and X-ray magnetic circular dichroism (XMCD) at the Cr L2,3 and Cr, Ti, and C K edges were investigated theoretically. The calculated results are in good agreement with experimental data. The effect of the electric quadrupole E2 and magnetic dipole M1 transitions at the Cr K edge has been investigated.
在考虑强库仑关联(GGA+U)的密度泛函理论框架下,在完全相对论自旋极化狄拉克线性松松锡轨道(LMTO)带结构方法的框架下,利用广义梯度近似(GGA)研究了T2AlC (T = Ti和Cr)化合物的电子和磁性能。从理论上研究了Cr L2,3和Cr, Ti, ck边缘的x射线吸收光谱和x射线磁圆二色性。计算结果与实验数据吻合较好。研究了电四极子E2和磁偶极子M1在Cr - K边缘的跃迁效应。
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引用次数: 0
Statistical theory of individual activity coefficients of electrolytes including multiple ionic charges 包含多个离子电荷的电解质的单个活度系数的统计理论
IF 0.6 4区 物理与天体物理 Q4 PHYSICS, CONDENSED MATTER Pub Date : 2023-05-25 DOI: 10.5488/CMP.26.23602
W. Ebeling, H. Krienke
In previous work we developed a new statistical method for calculating the individual activities of ions including the association of ions. Here we study multi-particle electrostatic interactions connected within higher cluster integrals and identify the ionization constants of the mass action law of associating ion clusters. In contrast to Bjerrum and Fuoss, our concept of association is not based on spatial criteria, but instead on the strength of interaction measured in powers of the Bjerrum parameter (e2/D0kBTa; a is contact) and defined by asymptotic properties of the cluster integrals. For ion pair formation our mass action constant is the classical counterpart of Planck's famous hydrogenic partition function. As a rule, the new association constants are smaller than traditional expressions, e.g., by Fuoss and Kraus, in the interesting regions of interaction parameters about fifty percent. Several examples including CaCl2, MgCl2, Na2SO4, K2SO4, LaCl3 and a model of seawater are studied. For several associating electrolytes and seawater, reasonable agreement with experiments and Monte Carlo results is achieved.
在以前的工作中,我们开发了一种新的统计方法来计算离子的单个活性,包括离子的结合。本文研究了连接在高簇积分内的多粒子静电相互作用,并确定了缔合离子簇质量作用定律的电离常数。与Bjerrum和Fuoss不同,我们的关联概念不是基于空间标准,而是基于Bjerrum参数(e2/D0kBTa;A是接触),由聚类积分的渐近性质定义。对于离子对的形成,我们的质量作用常数是普朗克著名的氢配分函数的经典对应。作为一个规则,新的关联常数比传统的表达式小,例如,由Fuoss和Kraus,在相互作用参数的有趣区域约50%。研究了CaCl2、MgCl2、Na2SO4、K2SO4、LaCl3等实例和海水模型。对于几种与海水相结合的电解质,得到了与实验和蒙特卡罗计算结果较为吻合的结果。
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引用次数: 0
Development of a new force field for the family of primary aliphatic amines using the three steps systematic parameterization procedure 用三步系统参数化方法建立了伯脂肪胺族的新力场
IF 0.6 4区 物理与天体物理 Q4 PHYSICS, CONDENSED MATTER Pub Date : 2023-05-25 DOI: 10.5488/CMP.26.23603
H. Espinosa-Jim'enez, A. B. Salazar-Arriaga, H. Domínguez
The applicability of the three steps systematic parametrization procedure (3SSPP) to develop a force field for primary amines was evaluated in the present work. Previous simulations of primary amines show that current force fields (FF) can underestimate some experimental values under room conditions. Therefore, we propose a new set of parameters, for an united atom (UA) model, that can be used for short and long amines which predict correctly thermodynamic and dynamical properties. Following the 3SSPP methodology, the partial charges are chosen to match the experimental dielectric constant whereas the Lennard-Jones (LJ) parameters, ε and σ, are fitted to reproduce the surface tension at the vapor-liquid interface and the liquid density, respectively. Simulations were initially conducted for the propylamine molecule by introducing three different types of carbon atoms, Cα and Cβ, with electric charges, and Cn, without charge. Then, modifying the charges of the carbons and using the transferable LJ parameters, the new set of constants for long amines were found. The results show good agreement for the experimental dielectric constant and mass density with a percentage error less than 1% surface tension the error is up to 4% ethylamine, the new charges were obtained from a fitting function calculated from the long amines results. For these molecules, the values of the dielectric constant and the surface tension present errors of the order of 10% with the experimental data. Miscibility of the amines was also tested with the new parameters and the results show reasonable agreement with experiments.
本文评价了三步系统参数化法(3SSPP)在建立伯胺力场中的适用性。以往对伯胺的模拟表明,在室温条件下,电流力场(FF)会低估某些实验值。因此,我们提出了一组新的参数,用于统一原子(UA)模型,可以正确预测短胺和长胺的热力学和动力学性质。根据3SSPP方法,选择部分电荷来匹配实验介电常数,并拟合Lennard-Jones (LJ)参数ε和σ来分别再现气液界面处的表面张力和液体密度。通过引入带电荷的Cα和Cβ以及不带电荷的Cn三种不同类型的碳原子,对丙胺分子进行了模拟。然后,通过改变碳的电荷并利用可转移的LJ参数,得到了长胺的一组新的常数。结果表明,实验介质常数和质量密度符合较好,表面张力误差小于1%,乙胺的表面张力误差高达4%,新电荷是由长胺结果计算的拟合函数得到的。对于这些分子,介电常数和表面张力值与实验数据存在10%左右的误差。用新参数对胺类化合物的混相进行了测试,结果与实验结果吻合较好。
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引用次数: 0
Spectral properties of a broadband far infrared photodetector with a new design of active region 一种新型有源区设计的宽带远红外探测器的光谱特性
IF 0.6 4区 物理与天体物理 Q4 PHYSICS, CONDENSED MATTER Pub Date : 2023-05-25 DOI: 10.5488/CMP.26.23705
M. Tkach, J. Seti, O. Voitsekhivska, V. Hutiv
A quantum theory of spectral parameters and oscillator strengths of quantum transitions in an active region, which contains cascades of wide quantum wells with a complicated potential profile is developed. A new spatial design of the cascade is calculated and proposed with such an asymmetric arrangement of the wells and barriers, in which, without an applied electric bias, the magnitudes of oscillator strengths are considerable and one-way resonant-tunneling transport of electrons is observed. As a result, it becomes possible to ensure a successful functioning of the broadband photodetector in the far IR range.
提出了一种包含具有复杂势分布的宽量子阱级联的有源区域中量子跃迁的谱参数和振子强度的量子理论。利用这种阱和势垒的不对称排列,计算并提出了一种新的级联空间设计,在没有施加电偏置的情况下,振荡强度的大小相当大,并且观察到电子的单向共振隧穿输运。因此,有可能确保宽带光电探测器在远红外范围内的成功运作。
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引用次数: 0
Structure and properties of the films based on ternary transition metal borides: theory and experiment 三元过渡金属硼化物薄膜的结构与性能:理论与实验
IF 0.6 4区 物理与天体物理 Q4 PHYSICS, CONDENSED MATTER Pub Date : 2023-05-25 DOI: 10.5488/CMP.26.22701
A. Onoprienko, V. Ivashchenko, V. Shevchenko
The review presents the results of theoretical and experimental studies of the structure, bonding between atoms, mechanical properties, thermal stability, and oxidation and corrosion resistance of films based on ternary transition metal borides.
本文综述了基于三元过渡金属硼化物薄膜的结构、原子间键合、力学性能、热稳定性、抗氧化性和耐腐蚀性等方面的理论和实验研究结果。
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引用次数: 0
Modelling thermoresponsive polymer brush by mesoscale computer simulations 热敏聚合物刷的中尺度计算机模拟
IF 0.6 4区 物理与天体物理 Q4 PHYSICS, CONDENSED MATTER Pub Date : 2023-04-14 DOI: 10.5488/CMP.26.33302
D. Yaremchuk, O. Kalyuzhnyi, J. Ilnytskyi
We consider a functional surface comprising thermoresponsive polymer chains, the material that has found numerous technological and biomedical applications. However, to achieve the required time and length scales for computer modelling of such applications, one is compelled to use coarse-grained mesoscopic modelling approaches. The model used here is based on the previous work [Soto-Figueroa et al., Soft Matter, 8, 1871 (2012)], and it mimics the principal feature of the poly(N-iso-propylacrylamide) (PNIPAM), namely, the rapid change of its hydrophilicity at the lower critical solution temperature (LCST). For the case of an isolated chain, we discuss scaling properties of the radius of gyration, end-to-end distance, various distribution functions, and the density profile of monomers below and above the LCST. For the case of the model thermoresposive brush, we search for the optimum grafting density at which the change in the brush height, upon crossing the LCST, reaches its maximum value. The interpretation of the thermoresponse, in terms of the Alexander-de Gennes blobs and the level of solvation of polymer chains in a brush, is provided.
我们考虑一个包含热敏聚合物链的功能表面,这种材料已经发现了许多技术和生物医学应用。然而,为了达到计算机模拟此类应用所需的时间和长度尺度,人们不得不使用粗粒度的介观建模方法。本文使用的模型基于先前的工作[Soto-Figueroa et al., Soft Matter, 8,1871(2012)],它模拟了聚n -异丙基丙烯胺(PNIPAM)的主要特征,即在较低临界溶液温度(LCST)下其亲水性的快速变化。在孤立链的情况下,我们讨论了旋转半径、端到端距离、各种分布函数和单体密度分布的标度性质。对于模型热响应电刷,我们寻找最佳接枝密度,使电刷高度的变化在穿过LCST时达到最大值。热响应的解释,在亚历山大-德热讷blobs和聚合物链的溶剂化水平的刷子,提供。
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引用次数: 1
Neutral band gap of carbon by quantum Monte Carlo methods 用量子蒙特卡罗方法研究碳中性带隙
IF 0.6 4区 物理与天体物理 Q4 PHYSICS, CONDENSED MATTER Pub Date : 2023-03-31 DOI: 10.5488/CMP.26.33701
V. Gorelov, Yubo Yang, M. Ruggeri, D. Ceperley, C. Pierleoni, M. Holzmann
We present a method of calculating the energy gap of a charge-neutral excitation using only ground-state calculations. We report Quantum Monte Carlo calculations of Γ→ Γ and Γ → X particle-hole excitation energies in diamond carbon. We analyze the finite-size effect and find the same 1/L decay rate as that in a charged excitation, where L is the linear extension of the supercell. This slow decay is attributed to the delocalized nature of the excitation in supercells too small to accommodate excitonic binding effects. At larger system sizes, the apparent 1/L decay crosses over to a 1/L3 behavior. Estimation of the scale of exciton binding can be used to correct finite-size effects of neutral gaps.
我们提出了一种仅使用基态计算来计算电荷中性激发能隙的方法。本文报道了金刚石碳中Γ→Γ和Γ→X粒子-空穴激发能的量子蒙特卡罗计算。我们分析了有限尺寸效应,发现了与带电激励相同的1/L衰减率,其中L是超级单体的线性延伸。这种缓慢的衰减归因于超细胞中激发的离域性质,超细胞太小而无法容纳激子结合效应。在较大的系统尺寸下,明显的1/L衰减跨越到1/L3行为。激子结合尺度的估计可用于修正中性间隙的有限尺寸效应。
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引用次数: 1
Merging of Dirac points through uniaxial modulation on an optical lattice 光学晶格上单轴调制狄拉克点的合并
IF 0.6 4区 物理与天体物理 Q4 PHYSICS, CONDENSED MATTER Pub Date : 2023-03-03 DOI: 10.5488/CMP.26.13503
A. López, B. Montañes, Ernesto Antonio Medina Dagger
We analyze the scenario of modulating the potential strength of bound atoms in an optical honeycomb lattice patterned by an electric field to emulate uniaxial strain. This modulation can be achieved by a combination of the strength of the patterned electric field and gauge vector effects using the Floquet approach. We show that such a modulation allows one to follow through a topological transition between a semi-metal and a band insulator, when two non-equivalent K points merge as a function of the electric field strength. We explicitly compute the wavefunctions for the moving K points and the Chern numbers up to the transition. Anisotropic effective masses and the insulating gap are described close to the semimetal-insulator transition.
我们分析了用电场模拟单轴应变来调制光学蜂窝晶格中束缚原子的电位强度的方案。这种调制可以通过结合图案化电场的强度和使用Floquet方法的规范矢量效应来实现。我们表明,当两个非等效K点作为电场强度的函数合并时,这种调制允许人们在半金属和带绝缘体之间进行拓扑跃迁。我们明确地计算了移动K点的波函数和一直到过渡的陈氏数。各向异性有效质量和绝缘间隙被描述为接近半金属-绝缘体转变。
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引用次数: 0
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Condensed Matter Physics
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