外界电场激励下的耦合FitzHugh-Nagumo神经元系统的放电节律研究

研究了单向耦合连接的两个FitzHugh-Nagumo神经元系统的动力学行为.随外激频率的变化,系统表现出p:q锁相（一种周期振荡,q周期刺激产生p周期动作电位）,且锁相是否发生与放电状态有关.研究表明外激频率和耦合强度都可以引起系统峰峰间期（interspike Interval,ISI）分岔,而外激频率对系统放电节律的影响更为明显,研究还发现混沌态是其他放电状态的过渡态. 关键词： FHN神经元 耦合 动力学行为     

Plasma in a metal layer exposed to an RF electric field

The response of electrons in a metal layer (sheet) to a variable electric field normal to the surface is studied under resonance conditions, i.e., when the frequency of the field is close to the plasma oscillation frequency. The electromagnetic field energy absorbed in the sheet is calculated.     

A new type of phonon instability in semiconductors exposed to a strong electric field

The damping of a phonon γ_q is calculated for the case when the electron acceleration influenced by a strong electric field for the time of the electron-phonon interaction is essential.     

三氯甲烷在外电场中的物理性质研究

三氯甲烷是挥发性卤代烃,可通过皮肤接触、呼吸或饮水进入人体,危害人体健康,其物理性质的进一步研究对于保护环境与人体健康十分重要.本文采用DFT(密度泛函理论)计算方法,在B3PW91/6-311G+(2d, p)基组水平下对三氯甲烷分子进行优化,从分子结构角度研究了不同外电场作用下,三氯甲烷分子的总能量,键长,电偶极矩,解离势能面,隧穿电离和红外光谱.计算结果表明,随着外加电场的增大,分子键长逐渐增长,偶极矩也随之增加,然而分子的总能量却逐渐减小.分子的最低空轨道能量与最高占据轨道能量之间的能隙也随着外加电场的增大而降低.分子的解离能在增加的电场条件下逐渐降低,吸收光谱的IR强度也有明显的变化.上述的计算结果为利用电场降解三氯甲烷提供重要的理论参考.     

外电场作用下C6H6的分子结构及其特性

采用 B3P86方法计算了C6H6在外电场作用下分子系统的能量及分子轨道能级、谐振频率、CH键离解能和极化率等分子特性;通过跃迁矩阵元计算了各激发态的激发能,吸收及自发辐射系数,从而进一步分析了苯分子的外场效应.对于高分子化合物尤其是具有苯环结构的有机高分子化合物的外场作用特性的研究具有参考价值.     

金纳米流体的电场可调光学性质

利用多次还原法制备了不同粒径的金纳米颗粒,SEM和粒度分析表明其平均粒径分别为11 nm,35 nm和58 nm.进一步通过表面活性剂辅助的液相转移法制备出不同粒径的油基金纳米流体,测试了金纳米流体在电场作用下的光学性质.结果表明金纳米流体在电场作用下表现出明显的双折射现象,且随电场强度的变化双折射具有可调节性.金颗粒粒径和浓度对折射率有明显影响,在实验采用的浓度范围内,折射率随金颗粒浓度和粒径的增加而减小.最后,利用电流变液结构转变机理对金纳米流体的电致双折射进行了分析. 关键词： 纳米流体 双折射 电流变液     

外场下SnS分子结构及其特性

对S原子采用6-311++G**基组,Sn原子采用SDB-cc-pVTZ基组,利用密度泛函(B3P86)方法对SnS分子进行了基态结构优化,并研究了外场作用下SnS基态分子键长、能量、能级分布、电荷布居分布、谐振频率和红外谱强度的影响规律.然后利用含时密度泛函(TD-B3P86)方法研究了SnS分子在外场下的激发特性.结果表明,在所加的电场范围内(-0.04 a.u.-0.04 a.u.),随着正向电场的增大,分子键长和红外谱强度均是先减小后增大;总能E,SnS基态分子的最高已占据轨道能量EH和谐振频率均是先增大后减小;分子的最低未占空轨道能量EL和能隙Eg均随正向电场的增大而减小.随着正向电场的增大,SnS分子由基态至前9个单重激发态跃迁的波长增大,激发能则减小.     

Magnetoelectric properties in A-type antiferromagnet in an electric field

Mean-field theory based on Heisenberg model is used to investigate the magnetic and magnetoelectric properties at a finite temperature in the A-type antiferromagnetic lattice, in which we consider that an applied electric field can generate a bulk magnetic moment. We have calculated the magnetic moment, magnetic susceptibility and magnetoelectric susceptibility as a function of temperature for A-type antiferromagnetic system. It is demonstrated that an applied electric field together with the coupling parameter has an effect on the magnetic ordering behavior. Our results are almost consistent with those of spin-wave theory within the range of low temperature.     

Focusing properties of the electric field between charged conical surfaces

The focusing properties of the electrostatic field between two charged conical surfaces are considered. An expression is obtained for the electric field intensity in the capacitor formed by two concentric circular cones with parallel generatrices. The equations of motion of an electron in such a capacitor are solved numerically, and it is shown that first-order focusing can be accomplished in it under specified conditions.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 35–40, October, 1981.     

外电场作用下ZnO分子的结构特性研究

本文以6-311++g(d,p)为基组, 采用密度泛函理论的B3P86方法优化得到了ZnO分子的基态稳定构型, 并计算了不同外电场(-0.05–0.05a.u.)下ZnO基态分子的稳定电子结构, 研究外电场对ZnO基态分子键长、总能量、电荷分布、能级分布、能隙及红外光谱的影响. 结果表明: 外加电场的大小和方向对分子结构和电子特性均有明显影响. 随着正向外加电场的增加, ZnO基态分子的平衡键长先减小后增加, 而分子总能量、振动频率和红外光谱的强度均先增加后减小. 分子的最高占据轨道能量E_H、最低未占据轨道能量E_L和能隙E_g始终处于减小趋势, 因而占据轨道的电子更容易被激发至空轨道. 这一结果可为ZnO分子的电致发光机理研究提供一定的理论参考. 关键词： ZnO 外电场 结构参数 激发     

几种硝基苯类炸药在外电场作用下的分子特性

采用密度泛函理论中的B3LYP方法,在6-31G*水平上研究了外电场对一些硝基苯类炸药分子的总能量、偶极矩、分子轨道能级和前线轨道能量差等分子特性的影响;考察了在外电场作用下分子前线轨道能量差与炸药的电火花感度之间的关系.结果表明,在外电场作用下分子总能量降低,偶极矩增大、前线轨道能量差减小;分子前线轨道能量差与炸药的电火花感度之间几乎线性相关,且外电场对这种线性相关性无明显影响.     

Spectra and dissociation properties of Freon 31 under electric field

Freon 31 is a carcinogenic substance. It is of great significance for studying its degradation under external electric field. The bond length, energy, dipole moment, orbital energy lever distribution, infrared spectra, and dissociation properties of Freon 31 molecule under the external field are investigated using the density functional theory on basis set level of B3LYP/6-311++G(d, p). In addition, the effects of electric field on ultraviolet–visible absorption spectra of the molecule are studied with CIS/6-311G++(d, p) method. The results indicate that spectra and dissociated properties under electric field have changed significantly. As the electric field (0–0.04 atomic units) along negative direction of y-axis increases, the bond length of carbon–chlorine bond gradually increases and tends to break; the bond length of carbon–fluorine bond gradually decreases. The energy gap first increases and then decreases changing with electric field. The infrared spectra and ultraviolet–visible absorption spectra exhibit blue shift or bathochromic shift under electric field. Moreover, the potential energy surface of Freon 31 about Carbon–Chlorine bond is scanned by the same basis set with configuration interaction - single excitation (CIS) method. The result shows the barrier of dissociation gradually decreases with the electric field. When the intensity of electric field is equal to 0.04 atomic units, the barrier has disappeared. In addition, the molecule is induced to fragmentation due to carbon–chlorine bond breaking. The results offer important reference to the degradation of contaminants.     

Influence of strain and electric field on the properties of silicane

We investigate the influence of strain and electric field on the properties of a silicane sheet. Some elastic parameters of silicane, such as an in-plane stiffness of 52.55 N/m and a Poisson’s ratio of 0.24, are obtained by calculating the strain energy. Compared with silicene, silicane is softer because of its relatively weaker Si-Si bonds. The band structure of silicane is tunable by a uniform tensile strain, with the increase of which the band gap decreases monotonously. Moreover, silicane undergoes an indirect-direct gap transition under a small strain, and a semiconductor-metal transition under a large strain. The electric field can change the Si-H bond length of silicane significantly. When a strong field is applied, the H atom at the high potential side becomes desorbed, while the H atom at the low potential side keeps bonded. So an external electric field can help to produce single-side hydrogenated silicene from silicane. We believe this study will be helpful for the application of silicane in the future.     

Electrical and structural properties of VO2 in an electric field

We examined the electrical and local structural properties of a VO₂ film at different electric fields using electrical resistance and x-ray absorption fine structure (XAFS) measurements at the V K edge in the temperature range of 30–100 °C. The T_c value of the metal-to-insulator transition (MIT) during both heating and cooling decreases with electric field. When the electric field exceeds a certain value, the MIT becomes sharper due to Joule heating. The MIT, the structural phase transition (SPT), and the pre-edge peak transition of the VO₂ do not congruently occur at a uniform temperature. A metallic VO₂ is observed in only the rutile (or M2) symmetry. An electric field induces a substantial amount of conduction electrons in insulating VO₂. Simultaneously measured resistance and XAFS reveal that Joule heating caused by an external electric field significantly affects the MIT and SPT of VO₂.     

Transport properties of AB-stacked bilayer graphene nanoribbons in an electric field

The electronic and thermal properties of AB-stacked bilayer graphene nanoribbons subject to the influences of a transverse electric field are investigated theoretically, including their transport properties. The dispersion relations are found to exhibit a rich dependence on the interlayer interactions, the field strength, and the geometry of the layers. The interlayer coupling will modify the subband curvature, create additional band-edge states, change the subband spacing or energy gap, and separate the partial flat bands. The bandstructures will be symmetric or asymmetric about the Fermi energy for monolayer or bilayer nanoribbons, respectively. The inclusion of a transverse electric field will further alter the bandstructures and lift the degeneracy of the partial flat bands. The chemical-potential-dependent electrical and thermal conductance exhibit a stepwise increase behavior. Variations in the electronic structures with field strength will be reflected in the electrical and thermal conductance. Prominent peaks, as well as single-shoulder and multi-shoulder structures in the electrical and thermal conductance are predicted when varying the electric field strength. The features of the conductance are found to be strongly dependent on the field strength, the geometry, interlayer interactions and temperature.     

外电场下甲醛的分子光谱与解离特性研究

摘要：以CC-PVQZ为基组,采用筛选的B3LYP研究了不同外电场对CH2O分子基态结构、电荷分布、总能量、电偶极距、最高占据轨道(HOMO)能级、最低占据轨道(LUMO)能级、能隙、红外光谱、拉曼光谱及CH2O分子中1C-2H键解离的影响。研究表明：电场由-0.04 a.u.变化至0.04 a.u.时,CH2O的结构参数与电场有明显依赖关系;体系总能量呈下降趋势;偶极矩呈增加趋势;HOMO能级与LUMO能级均逐步降低;能隙则呈增加趋势,即CH2O参与化学反应的能力会受到电场的影响;红外与拉曼光谱在电场考察范围内均出现红移现象,且光谱强度还会受到电场的影响,即可利用电场对分子的红外及拉曼光谱进行调控,从而便于对相关谱图信息的捕捉;CH2O分子中的1C-2H键的束缚情况会受不同电场的影响,且1C-2H键解离势垒与电场具有极高相关性,研究结果为电场降解甲醛提供了重要的理论依据。     

外电场下二氧化锆的分子结构及其特性

对O原子采用6-311++G*基组,Zr原子采用aug-cc-pVTZ-PP基组,利用密度泛函(B3P86)方法优化得到了ZrO2分子的稳定构型,并研究了不同外电场(0—0.025 a.u.)作用下ZrO2基态分子键长、能量、电荷分布、偶极矩和能级的变化规律.在优化构型的基础上,利用含时密度泛函(TD-B3P86)方法研究了ZrO2分子在外电场作用下前6个激发态的激发能、跃迁波长和振子强度的激发特性.研究结果表明:随着电场强度的增大,Zr—2O的键长增大,而Zr—3O的键长均匀减少,总能量降低,偶极矩增大;最高占据轨道能量基本保持不变,最低未占据轨道和能隙均减小.电场的增大使得激发能减小,各个激发态跃迁波长均发生不同程度的红移现象,因而,利用外电场可以控制ZrO2的发光光谱范围在可见-红外区域扩展.