We study the dynamics of a driven spherical colloidal particle moving in a fluid with a broken rotational symmetry. Using a nematic liquid crystal as a model, we demonstrate that when the applied force is not aligned along or perpendicular to the orientational order, the colloidal velocity does not align with the force, but forms an angle with respect to the pulling direction. This leads to blue an anisotropic hydrodynamic drag tensor which depends on the material parameters. In the case of nematic liquid crystal, we give an analytical expression and discuss the resulting implications for active microrheology experiments on fluids with broken rotational symmetry.
{"title":"Active microrheology of fluids with orientational order","authors":"J. Lintuvuori, A. Würger","doi":"10.5488/CMP.27.13801","DOIUrl":"https://doi.org/10.5488/CMP.27.13801","url":null,"abstract":"We study the dynamics of a driven spherical colloidal particle moving in a fluid with a broken rotational symmetry. Using a nematic liquid crystal as a model, we demonstrate that when the applied force is not aligned along or perpendicular to the orientational order, the colloidal velocity does not align with the force, but forms an angle with respect to the pulling direction. This leads to blue an anisotropic hydrodynamic drag tensor which depends on the material parameters. In the case of nematic liquid crystal, we give an analytical expression and discuss the resulting implications for active microrheology experiments on fluids with broken rotational symmetry.","PeriodicalId":10528,"journal":{"name":"Condensed Matter Physics","volume":null,"pages":null},"PeriodicalIF":0.6,"publicationDate":"2024-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140387986","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The electronic properties as well as the structural characteristics and their pressure dependence of the semi-metallic B10-structured compound InBi were investigated. It is found that the structural values of InBi calculated in the first-principles calculations reproduce the experimental values worse than those for other heavy III-V pnictides, which are characterized by cubic B3 and B2 structures, as well as for IV-VI compounds SnO and PbO having the same B10 structure. The low accuracy of the first-principles calculations is a consequence of the peculiarities of the band structure inherent to InBi and not observed in all the other above-mentioned compounds. To improve the agreement with the experiment, it is proposed to take into account the distortion of the compensated half-metal condition at the highly symmetric points of the Brillouin zone, where the electronic and hole pockets are located.
{"title":"Study of the structural and electronic properties of semimetallic InBi: first-principles calculation of compound with peculiarities of the electronic structure","authors":"V. V. Pozhyvatenko","doi":"10.5488/CMP.26.43601","DOIUrl":"https://doi.org/10.5488/CMP.26.43601","url":null,"abstract":"The electronic properties as well as the structural characteristics and their pressure dependence of the semi-metallic B10-structured compound InBi were investigated. It is found that the structural values of InBi calculated in the first-principles calculations reproduce the experimental values worse than those for other heavy III-V pnictides, which are characterized by cubic B3 and B2 structures, as well as for IV-VI compounds SnO and PbO having the same B10 structure. The low accuracy of the first-principles calculations is a consequence of the peculiarities of the band structure inherent to InBi and not observed in all the other above-mentioned compounds. To improve the agreement with the experiment, it is proposed to take into account the distortion of the compensated half-metal condition at the highly symmetric points of the Brillouin zone, where the electronic and hole pockets are located.","PeriodicalId":10528,"journal":{"name":"Condensed Matter Physics","volume":null,"pages":null},"PeriodicalIF":0.6,"publicationDate":"2024-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139526666","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study is aimed at exploring the electronic, magnetic, and magneto-optical properties of double perovskites Ca2FeIrO6 and Ca2CoIrO6 with monoclinic structure (space group P21/c) in order to examine their potential applications in spintronic and photovoltaic devices. The calculations were done using the full-potential linearized augmented plane wave within the density functional theory. For the electronic exchange-correlation function, we used the generalized gradient approximation (GGA) and GGA+U (Hubbard potential), and spin-orbit coupling (SOC). The study showed that Ca2FeIrO6 and Ca2CoIrO6 exhibit a monoclinic structure (space group P21/c). The structure relaxation shows an antiferromagnetic behavior in both systems with a magnetic moment of about 6.00 μB for Ca2FeIrO6 and 4.00 μB for Ca2CoIrO6 by using GGA+U approximation. The results of GGA and GGA+U predict the half-metallic behavior of Ca2FeIrO6 and Ca2CoIrO6. The magneto-optical polar Kerr effect (MOKE) was examined by studying the variation of Kerr and ellipticity rotation. The Kerr rotation angle is 1.3º at 4.82 eV and -1.21º at 4.3 eV, and the ellipticity angle is -1.21º at 4.3 eV for Ca2FeIrO6. In the case of Ca2CoIrO6, the Kerr rotation angle is -1.04º at 4.05 eV; the significant Kerr rotation in both compounds may suggest the application of these materials in optoelectronics bias. The named compounds have a potential application in the field of spintronics and its devices, such as in optoelectronics technologies.
本研究旨在探索具有单斜结构（空间群 P21/c）的双过氧化物 Ca2FeIrO6 和 Ca2CoIrO6 的电子、磁性和磁光特性，以研究它们在自旋电子和光伏设备中的潜在应用。计算采用密度泛函理论中的全电位线性化增强平面波。对于电子交换相关函数，我们使用了广义梯度近似（GGA）和 GGA+U（哈伯德势）以及自旋轨道耦合（SOC）。研究表明，Ca2FeIrO6 和 Ca2CoIrO6 呈现单斜结构（空间群 P21/c）。通过使用 GGA+U 近似法，结构弛豫显示这两个体系都具有反铁磁性，Ca2FeIrO6 的磁矩约为 6.00 μB，Ca2CoIrO6 的磁矩约为 4.00 μB。GGA 和 GGA+U 的结果预测了 Ca2FeIrO6 和 Ca2CoIrO6 的半金属行为。通过研究克尔旋转和椭圆旋转的变化，研究了磁光极性克尔效应（MOKE）。对于 Ca2FeIrO6，4.82 eV 时的克尔旋转角为 1.3º，4.3 eV 时为-1.21º，4.3 eV 时的椭圆度角为-1.21º。在 Ca2CoIrO6 中，4.05 eV 时的克尔旋转角为-1.04º；这两种化合物中显著的克尔旋转可能暗示着这些材料在光电子偏压方面的应用。上述化合物在自旋电子学及其器件（如光电子技术）领域具有潜在的应用前景。
{"title":"Exploring the structural, electronic, magnetic, and magneto-optical properties of double perovskites Ca2TMIrO6 (TM = Fe, Co) through first principles study","authors":"I. Touaibia, A. Bouguerra, W. Guenez, F. Chemam","doi":"10.5488/CMP.26.43702","DOIUrl":"https://doi.org/10.5488/CMP.26.43702","url":null,"abstract":"This study is aimed at exploring the electronic, magnetic, and magneto-optical properties of double perovskites Ca2FeIrO6 and Ca2CoIrO6 with monoclinic structure (space group P21/c) in order to examine their potential applications in spintronic and photovoltaic devices. The calculations were done using the full-potential linearized augmented plane wave within the density functional theory. For the electronic exchange-correlation function, we used the generalized gradient approximation (GGA) and GGA+U (Hubbard potential), and spin-orbit coupling (SOC). The study showed that Ca2FeIrO6 and Ca2CoIrO6 exhibit a monoclinic structure (space group P21/c). The structure relaxation shows an antiferromagnetic behavior in both systems with a magnetic moment of about 6.00 μB for Ca2FeIrO6 and 4.00 μB for Ca2CoIrO6 by using GGA+U approximation. The results of GGA and GGA+U predict the half-metallic behavior of Ca2FeIrO6 and Ca2CoIrO6. The magneto-optical polar Kerr effect (MOKE) was examined by studying the variation of Kerr and ellipticity rotation. The Kerr rotation angle is 1.3º at 4.82 eV and -1.21º at 4.3 eV, and the ellipticity angle is -1.21º at 4.3 eV for Ca2FeIrO6. In the case of Ca2CoIrO6, the Kerr rotation angle is -1.04º at 4.05 eV; the significant Kerr rotation in both compounds may suggest the application of these materials in optoelectronics bias. The named compounds have a potential application in the field of spintronics and its devices, such as in optoelectronics technologies.","PeriodicalId":10528,"journal":{"name":"Condensed Matter Physics","volume":null,"pages":null},"PeriodicalIF":0.6,"publicationDate":"2024-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139526829","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Using the path probability and lowest approximation of cluster variation method, we study the dynamic and equilibrium properties of a bilayer magnetic system, consisting of two ferromagnetic monolayers antiferromagnetically coupled for different spins (σ = 1/2 and S = 1). Firstly, numerical results of the monolayer and total magnetizations are presented under the effect of the diverse physical parameters, and the phase diagrams of bilayer system are discussed. Then, since it is well established that the path probability method is an effective method for the existence of metastable states, the time evolution of monolayer- and total magnetizations is investigated.
我们利用路径概率和最低近似簇变化方法，研究了由不同自旋（σ = 1/2 和 S = 1）反铁磁耦合的两个铁磁单层组成的双层磁系统的动态和平衡特性。首先，给出了在不同物理参数影响下的单层磁化和总磁化的数值结果，并讨论了双层体系的相图。然后，由于路径概率法是研究陨变态存在的有效方法，研究了单层磁化和总磁化的时间演化。
{"title":"Dynamic behavior of the antiferromagnetically coupled bilayer Ising model","authors":"C. Ekiz, R. Erdem, D. Semet","doi":"10.5488/CMP.26.43701","DOIUrl":"https://doi.org/10.5488/CMP.26.43701","url":null,"abstract":"Using the path probability and lowest approximation of cluster variation method, we study the dynamic and equilibrium properties of a bilayer magnetic system, consisting of two ferromagnetic monolayers antiferromagnetically coupled for different spins (σ = 1/2 and S = 1). Firstly, numerical results of the monolayer and total magnetizations are presented under the effect of the diverse physical parameters, and the phase diagrams of bilayer system are discussed. Then, since it is well established that the path probability method is an effective method for the existence of metastable states, the time evolution of monolayer- and total magnetizations is investigated.","PeriodicalId":10528,"journal":{"name":"Condensed Matter Physics","volume":null,"pages":null},"PeriodicalIF":0.6,"publicationDate":"2024-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139527063","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
I. S. Girnyk, B. Horon, V. B. Kapustianyk, O. S. Kushnir, R. Shopa
Temperature measurements of dielectric permittivity are performed for nonstoichiometric ferroelectric lead germanate Pb4.95Ge3O11 and multiferroic solid solution [N(C2H5)4]2CoClBr3. Unlike the heat capacity data, the analysis of the dielectric permittivity of ferroics is usually performed at the assumption that the dielectric `background' is negligible compared with its critical part. In this work we quantitatively interpret the dielectric properties of the single crystals mentioned above and the appropriate literature data for multiferroic Sr2IrO4 crystals, using generalized Curie-Weiss formulas that combine corrections due to a nonlinear temperature-dependent dielectric background, a modified critical index of electric susceptibility, and a diffuse character of phase transition. We argue that taking account of the temperature dependent dielectric background can improve notably the quantitative analysis of PTs for a number of classes of the ferroic materials.
{"title":"Nonlinear background corrections to dielectric permittivity of ferroics and multiferroics","authors":"I. S. Girnyk, B. Horon, V. B. Kapustianyk, O. S. Kushnir, R. Shopa","doi":"10.5488/CMP.26.43604","DOIUrl":"https://doi.org/10.5488/CMP.26.43604","url":null,"abstract":"Temperature measurements of dielectric permittivity are performed for nonstoichiometric ferroelectric lead germanate Pb4.95Ge3O11 and multiferroic solid solution [N(C2H5)4]2CoClBr3. Unlike the heat capacity data, the analysis of the dielectric permittivity of ferroics is usually performed at the assumption that the dielectric `background' is negligible compared with its critical part. In this work we quantitatively interpret the dielectric properties of the single crystals mentioned above and the appropriate literature data for multiferroic Sr2IrO4 crystals, using generalized Curie-Weiss formulas that combine corrections due to a nonlinear temperature-dependent dielectric background, a modified critical index of electric susceptibility, and a diffuse character of phase transition. We argue that taking account of the temperature dependent dielectric background can improve notably the quantitative analysis of PTs for a number of classes of the ferroic materials.","PeriodicalId":10528,"journal":{"name":"Condensed Matter Physics","volume":null,"pages":null},"PeriodicalIF":0.6,"publicationDate":"2024-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139527131","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Korotun, N. A. Smirnova, V. Reva, I. Titov, G. M. Shilo
The relations for the polarizability of the metallic nanoparticles, coated with the shell of cyanine dyes, are obtained in the article. The frequency dependencies for light absorption and scattering efficiencies, the heating of the composite nanoparticle and the electric field amplification in its neighborhood are studied. It is established that all the dependencies have three maxima which correspond to the frequencies of hybrid plasmon-exciton resonance. It is shown that an increase in content of metal in the nanoparticle causes a blue shift of the maxima from the visible part of the spectrum and a red shift of the maximum from ultraviolet frequency range. The issue of application of metal-organic nanoparticles in nanomedicine, in particular for the photothermal therapy of malignant neoplasms is studied.
{"title":"Optical and thermal effects in the neighborhood of the spherical layered nanoparticle of the ``metallic core – J-aggregate shell'' structure","authors":"A. Korotun, N. A. Smirnova, V. Reva, I. Titov, G. M. Shilo","doi":"10.5488/CMP.26.43704","DOIUrl":"https://doi.org/10.5488/CMP.26.43704","url":null,"abstract":"The relations for the polarizability of the metallic nanoparticles, coated with the shell of cyanine dyes, are obtained in the article. The frequency dependencies for light absorption and scattering efficiencies, the heating of the composite nanoparticle and the electric field amplification in its neighborhood are studied. It is established that all the dependencies have three maxima which correspond to the frequencies of hybrid plasmon-exciton resonance. It is shown that an increase in content of metal in the nanoparticle causes a blue shift of the maxima from the visible part of the spectrum and a red shift of the maximum from ultraviolet frequency range. The issue of application of metal-organic nanoparticles in nanomedicine, in particular for the photothermal therapy of malignant neoplasms is studied.","PeriodicalId":10528,"journal":{"name":"Condensed Matter Physics","volume":null,"pages":null},"PeriodicalIF":0.6,"publicationDate":"2024-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139527003","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The interactions between different layers in van der Waals heterostructures have a significant impact on the electronic and optical characteristics. By utilizing the intrinsic dipole moment of Janus transition metal dichalcogenides (TMDs), it is possible to tune these interlayer interactions. We systematically investigate structural and electronic properties of Janus MoSSe monolayer/graphene-like Aluminum Nitrides (MoSSe/g-AlN) heterostructures with point defects by employing density functional theory calculations with the inclusion of the nonlocal van der Waals correction. The findings indicate that the examined heterostructures are energetically and thermodynamically stable, and their electronic structures can be readily modified by creating a heterostructure with the defects in g-AlN monolayer. This heterostructure exhibits an indirect semiconductor with the band gap of 1.627 eV which is in the visible infrared region. It can be of interest for photovoltaic applications. When a single N atom or Al atom is removed from a monolayer of g-AlN in the heterostructure, creating vacancy defects, the material exhibits similar electronic band structures with localized states within the band gap which can be used for deliberately tailoring the electronic properties of the MoSSe/g-AlN heterostructure. These tunable results can offer exciting opportunities for designing nanoelectronics devices based on MoSSe/g-AlN heterojunctions.
范德华异质结构中不同层之间的相互作用对电子和光学特性有重大影响。通过利用 Janus 过渡金属二卤化物（TMD）的固有偶极矩，可以调整这些层间相互作用。我们采用密度泛函理论计算，并加入非局部范德华修正，系统地研究了具有点缺陷的 Janus MoSSe 单层/类石墨烯氮化铝（MoSSe/g-AlN）异质结构的结构和电子特性。研究结果表明，所研究的异质结构在能量和热力学上都是稳定的，而且它们的电子结构可以通过在 g-AlN 单层中创建带有缺陷的异质结构而轻易改变。这种异质结构是一种间接半导体，其带隙为 1.627 eV，处于可见红外区域。它可用于光伏应用。当从异质结构中的单层 g-AlN 中移除单个 N 原子或 Al 原子，产生空位缺陷时，材料会显示出类似的电子能带结构，并在能带隙内形成局部态，这可用于刻意调整 MoSSe/g-AlN 异质结构的电子特性。这些可调谐的结果为设计基于 MoSSe/g-AlN 异质结的纳米电子器件提供了令人兴奋的机会。
{"title":"The role of intrinsic atomic defects in a Janus MoSSe/XN (X = Al, Ga) heterostructure: a first principles study","authors":"Ö. C. Yelgel","doi":"10.5488/CMP.26.43703","DOIUrl":"https://doi.org/10.5488/CMP.26.43703","url":null,"abstract":"The interactions between different layers in van der Waals heterostructures have a significant impact on the electronic and optical characteristics. By utilizing the intrinsic dipole moment of Janus transition metal dichalcogenides (TMDs), it is possible to tune these interlayer interactions. We systematically investigate structural and electronic properties of Janus MoSSe monolayer/graphene-like Aluminum Nitrides (MoSSe/g-AlN) heterostructures with point defects by employing density functional theory calculations with the inclusion of the nonlocal van der Waals correction. The findings indicate that the examined heterostructures are energetically and thermodynamically stable, and their electronic structures can be readily modified by creating a heterostructure with the defects in g-AlN monolayer. This heterostructure exhibits an indirect semiconductor with the band gap of 1.627 eV which is in the visible infrared region. It can be of interest for photovoltaic applications. When a single N atom or Al atom is removed from a monolayer of g-AlN in the heterostructure, creating vacancy defects, the material exhibits similar electronic band structures with localized states within the band gap which can be used for deliberately tailoring the electronic properties of the MoSSe/g-AlN heterostructure. These tunable results can offer exciting opportunities for designing nanoelectronics devices based on MoSSe/g-AlN heterojunctions.","PeriodicalId":10528,"journal":{"name":"Condensed Matter Physics","volume":null,"pages":null},"PeriodicalIF":0.6,"publicationDate":"2024-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139527342","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The molecular dynamics simulations were used to obtain the radius of gyration of real ring polymer chains with different topological structures consisting of 360 monomers. We focus on the entropic force which is exerted by a dilute solution of ring polymer chains of different topological structures with the excluded volume interaction (EVI) in a good solvent on the confining parallel walls of a slit geometry. We consider mixed boundary conditions of one repulsive wall and the other one at the adsorption threshold. The obtained molecular dynamics simulation results for a wide slit region demonstrate a qualitative agreement with previous analytical results for ideal ring polymers. These results could lead to interesting potential applications in materials engineering and improve understanding of some biological processes suggested in the paper. Additionally, they could be applied in micro- and nano-electromechanical devices (MEMS and NEMS) in order to reduce the static friction.
{"title":"Entropic force in a dilute solution of real ring polymer chains with different topological structures in a slit of two parallel walls with mixed boundary conditions","authors":"P. Kuterba, Z. Danel, W. Janke","doi":"10.5488/CMP.26.43605","DOIUrl":"https://doi.org/10.5488/CMP.26.43605","url":null,"abstract":"The molecular dynamics simulations were used to obtain the radius of gyration of real ring polymer chains with different topological structures consisting of 360 monomers. We focus on the entropic force which is exerted by a dilute solution of ring polymer chains of different topological structures with the excluded volume interaction (EVI) in a good solvent on the confining parallel walls of a slit geometry. We consider mixed boundary conditions of one repulsive wall and the other one at the adsorption threshold. The obtained molecular dynamics simulation results for a wide slit region demonstrate a qualitative agreement with previous analytical results for ideal ring polymers. These results could lead to interesting potential applications in materials engineering and improve understanding of some biological processes suggested in the paper. Additionally, they could be applied in micro- and nano-electromechanical devices (MEMS and NEMS) in order to reduce the static friction.","PeriodicalId":10528,"journal":{"name":"Condensed Matter Physics","volume":null,"pages":null},"PeriodicalIF":0.6,"publicationDate":"2024-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139527008","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The lattice thermal conductivity of graphene is evaluated using a microscopic model that takes into account the lattice's discrete nature and the phonon dispersion relation within the Brillouin zone. The Boltzmann transport equation is solved iteratively within the framework of three-phonon interactions without taking into account the four-phonon scattering process. The Umklapp and normal collisions are treated rigorously, thereby avoiding relaxation-time and long-wavelength approximations. The mechanisms of the failures of these approximations in predicting the thermal transport properties are discussed. Evaluation of the thermal conductivity is performed at different temperatures and frequencies and in different crystallite sizes. Reasonably good agreement with the experimental data is obtained. The calculation reveals a critical role of out-of-plane acoustic phonons in determining the thermal conductivity. The out-of-plane acoustic phonons contribute greatly and the longitudinal and transverse acoustic phonons make small contributions over a wide range of temperatures and frequencies. The out-of-plane acoustic phonons dominate the thermal conductivity due to their high density of states and restrictions governing the anharmonic phonon scattering. The selection rule severely restricts the phase space for out-of-plane phonon scattering due to reflection symmetry. The optical phonon contribution cannot be neglected at higher temperatures. Both Umklapp and normal processes must be taken into account in order to predict the phonon transport properties accurately.
{"title":"Effect of out-of-plane acoustic phonons on the thermal transport properties of graphene","authors":"J. Chen, Y. Liu","doi":"10.5488/CMP.26.43603","DOIUrl":"https://doi.org/10.5488/CMP.26.43603","url":null,"abstract":"The lattice thermal conductivity of graphene is evaluated using a microscopic model that takes into account the lattice's discrete nature and the phonon dispersion relation within the Brillouin zone. The Boltzmann transport equation is solved iteratively within the framework of three-phonon interactions without taking into account the four-phonon scattering process. The Umklapp and normal collisions are treated rigorously, thereby avoiding relaxation-time and long-wavelength approximations. The mechanisms of the failures of these approximations in predicting the thermal transport properties are discussed. Evaluation of the thermal conductivity is performed at different temperatures and frequencies and in different crystallite sizes. Reasonably good agreement with the experimental data is obtained. The calculation reveals a critical role of out-of-plane acoustic phonons in determining the thermal conductivity. The out-of-plane acoustic phonons contribute greatly and the longitudinal and transverse acoustic phonons make small contributions over a wide range of temperatures and frequencies. The out-of-plane acoustic phonons dominate the thermal conductivity due to their high density of states and restrictions governing the anharmonic phonon scattering. The selection rule severely restricts the phase space for out-of-plane phonon scattering due to reflection symmetry. The optical phonon contribution cannot be neglected at higher temperatures. Both Umklapp and normal processes must be taken into account in order to predict the phonon transport properties accurately.","PeriodicalId":10528,"journal":{"name":"Condensed Matter Physics","volume":null,"pages":null},"PeriodicalIF":0.6,"publicationDate":"2024-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139527423","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this paper, we have studied the effect of doping of ZnO and MgO nanoparticles (NPs) in 4-(trans-4-n-hexylcyclo-hexyl) isothiocyanatobenzoate. A thorough comparison of dielectric properties, optoelectronic properties, and calorimetric phase transition properties has been done for MgO and ZnO NP doped LC. We prepare their homogenous mixture of MgO and ZnO NPs in toluene and transfer into cells made of glass and Indium Tin-Oxide (ITO) coated glass. The observed microstructures in the hybrid system can be classified into three main categories: grain like structures formed by aggregation of smaller size MgO nanoparticles while liquid crystal molecules anchor over the surfaces of nanoparticles, the grtu grain-like structures further integrate to form inorganic polymeric type of honeycomb-like mesostructures in presence of glass surface, and flower-like clusters of MgO nanoparticles on ITO surface. The smaller size nanoparticles can maintain the energy balance by allowing the anchoring of liquid crystal molecules over their surfaces whereas the larger size nanoparticles cannot compromise or maintain the energy balance with the liquid crystal molecules and are separated out to nucleate and form bigger size nanoaggregate or clusters. The energy preference of the substrate and nanoparticle’s surface to liquid crystal molecules plays an important role in the formation of different types of hierarchical nano- and microstructures. We account the reasons for the formation of nano and micro scale hierarchical structures on the basis of the competition between the forces: NP-NP, LC-LC, NP-LC, Glass/ITO-NP, and Glass/ITO-LC interactions. We observed a considerable change in the dielectric properties, transition temperature, bandgap, and other parameters of LC molecules when MgO NPs are doped, but a minor change occurs when ZnO NPs are doped in LC. Optical microscopy, FTIR, Raman, IR, HR-XRD and FESEM-EDX characterization data confirm and validate our guiding conceptions.
{"title":"Formation of nano and micro scale hierarchical structures in MgO and ZnO quantum dots doped LC media: the role of competitive forces","authors":"A. K. Singh, S. P. Singh","doi":"10.5488/CMP.26.43602","DOIUrl":"https://doi.org/10.5488/CMP.26.43602","url":null,"abstract":"In this paper, we have studied the effect of doping of ZnO and MgO nanoparticles (NPs) in 4-(trans-4-n-hexylcyclo-hexyl) isothiocyanatobenzoate. A thorough comparison of dielectric properties, optoelectronic properties, and calorimetric phase transition properties has been done for MgO and ZnO NP doped LC. We prepare their homogenous mixture of MgO and ZnO NPs in toluene and transfer into cells made of glass and Indium Tin-Oxide (ITO) coated glass. The observed microstructures in the hybrid system can be classified into three main categories: grain like structures formed by aggregation of smaller size MgO nanoparticles while liquid crystal molecules anchor over the surfaces of nanoparticles, the grtu grain-like structures further integrate to form inorganic polymeric type of honeycomb-like mesostructures in presence of glass surface, and flower-like clusters of MgO nanoparticles on ITO surface. The smaller size nanoparticles can maintain the energy balance by allowing the anchoring of liquid crystal molecules over their surfaces whereas the larger size nanoparticles cannot compromise or maintain the energy balance with the liquid crystal molecules and are separated out to nucleate and form bigger size nanoaggregate or clusters. The energy preference of the substrate and nanoparticle’s surface to liquid crystal molecules plays an important role in the formation of different types of hierarchical nano- and microstructures. We account the reasons for the formation of nano and micro scale hierarchical structures on the basis of the competition between the forces: NP-NP, LC-LC, NP-LC, Glass/ITO-NP, and Glass/ITO-LC interactions. We observed a considerable change in the dielectric properties, transition temperature, bandgap, and other parameters of LC molecules when MgO NPs are doped, but a minor change occurs when ZnO NPs are doped in LC. Optical microscopy, FTIR, Raman, IR, HR-XRD and FESEM-EDX characterization data confirm and validate our guiding conceptions.","PeriodicalId":10528,"journal":{"name":"Condensed Matter Physics","volume":null,"pages":null},"PeriodicalIF":0.6,"publicationDate":"2024-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139527214","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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