共查询到16条相似文献,搜索用时 140 毫秒
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具有在位势的一维双原子链晶格振动的色散关系 总被引:1,自引:1,他引:0
在简谐近似下,求解具有在位势的一维双原子链晶格振动运动方程,得到了具有在位势的晶格振动的色散关系.在位势使色散关系声频支在布里渊区中心的振动频率不再为零,并且随在位势的增大而增大.对于原子之间相互作用势不随在位势大小变化的情况下,晶格振动的色散关系的频隙随在位势的增大而变宽.讨论了原子链由只有在位势的不连续极限(AC极限),通过在位势逐渐减弱而原子间相互作用势逐渐增强,最后演变到只有原子间相互作用势的原子链的情况.随着在位势减弱和相互作用势增强,色散关系的频隙由AC极限的孤立轻、重原子简谐振动频率之差逐渐变化到通常的无在位势的色散关系频隙. 相似文献
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通过数值求解具有在位势的一维双原子链晶格振动的运动方程组,给出了具有不同大小在位势的长声学波振动模图像,直观展示出在位势使原胞中两种原子的振动位移不同,并且随在位势的增大,振动位移之差显著增大. 相似文献
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考虑原子间次近邻相互作用,讨论了具有在位势的一维双原子链中杂质引起的局域振动,得到次近邻互作用力、在位势共同作用下局域模的存在条件及振动的基本特征. 相似文献
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不同边界条件下一维双原子链的晶格振动 总被引:10,自引:2,他引:8
在自由边界条件和驻波边界条件下,讨论分析了一维双原子链晶格振动的振动模和色散关系,并与周期性边界条件下的结果进行了比较;明确了在不同边界条件下讨论实际原子链晶格振动的振动模和色散关系,其结果是相同的。 相似文献
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对具有在位势且含杂质的一维双原子链的晶格振动方程组进行求解,得到了局域振动的解析解, 给出了在位势对局域振动影响的基本特征,并简要讨论了局域模的存在形式. 相似文献
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In this paper we study the existence and stability of two-dimensional discrete gap
breathers in a two-dimensional diatomic face-centered square lattice
consisting of alternating light and heavy atoms, with on-site
potential and coupling potential. This study is focused on
two-dimensional breathers with their frequency in the gap that
separates the acoustic and optical bands of the phonon spectrum. We
demonstrate the possibility of the existence of two-dimensional gap
breathers by using a numerical method. Six types of two-dimensional
gap breathers are obtained, i.e., symmetric, mirror-symmetric and
asymmetric, whether the center of the breather is on a light or a
heavy atom. The difference between one-dimensional discrete gap
breathers and two-dimensional discrete gap breathers is also
discussed. We use Aubry's theory to analyze the stability of
discrete gap breathers in the two-dimensional diatomic face-centered
square lattice. 相似文献
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Parametric simultaneous solitary wave (simulton) excitations are shown to be possible in nonlinear lattices. Taking a one-dimensional diatomic lattice with a cubic potential as an example, we consider the nonlinear coupling between the upper cut-off mode of acoustic branch (as a fundamental wave) and the upper cut-off mode of optical branch (as a second harmonic wave). Based on a quasi-discreteness approach the Karamzin-Sukhorukov equations for two slowly varying amplitudes of the fundamental and the second harmonic waves in the lattice are derived when the condition of second harmonic generation is satisfied. The lattice simulton solutions are given explicitly and the results show that these lattice simultons can be nonpropagating when the wave vectors of the fundamental wave and the second harmonic waves are exactly at π/a (where a is the lattice constant) and zero, respectively. 相似文献
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We have calculated the phonon and periodon dispersion relations in IV–VI semi-conducting bulk PbTe and SnTe and their superlattice
structure. The model used here is a one-dimensional lattice which includes harmonic interactions up to second neighbours as
well as on-site nonlinear electron-ion interactions at the anion site. We calculate the phonon and periodon dispersion relations
in bulk and PbTe-SnTe superlattice for the transverse optic and acoustic modes using the transfer matrix method. Our analysis
has predicted correct nature of the folding of acoustic and confinement of optical phonons at various frequency intervals
corresponding to pass and stop bands of the superlattices. 相似文献
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杨慧 《原子与分子物理学报》2005,22(1):53-56
将聚二乙炔主链简化为有限的一维复式碳原子链,利用经典的晶格动力学方法研究了其色散关系.聚二乙炔链色散关系曲线由一支声学模和三支光学模组成,它们在波矢为零处及Brillouin zone(BZ)边界处拉开了间隙,弹性力常数的变化将显著地改变带宽和能隙. 相似文献
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A. S. Tchakoutio Nguetcho T. C. Kofane 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,57(4):411-422
The dynamics of protons in hydrogen-bonded quasi one-dimensional
networks are studied using a diatomic lattice model of protons and heavy ions
including a φ4 on-site substrate potential. It is shows that the model with
linear and nonlinear coupling of the quartic type between lattice sites for
the protons admits a richer dynamics that cannot be produced with linear
couplings alone. Depending on two types of physical boundary conditions, namely
of the drop or condensate type, and on conditions requiring the presence of
linear and nonlinear dispersion terms, soliton patterns of compact support,
whether with a peak, drop, bell, cusp, shock, kink, bubble or loop structure,
are obtained within a continuum approximation. Phase trajectories as well as analytical
studies provide information on the disintegration of soliton patterns upon
reaching some critical values of the lattice parameters. The total energies
of soliton patterns are computed exactly in the continuum limit. We also
show that when anharmonic interactions of the phonon are taken into account, the width and
energy of soliton patterns are in qualitative agreement with
experimental data. 相似文献
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Under harmonic approximation, this paper discusses the
linear dispersion relation of the one-dimensional chain. The existence
and evolution of discrete breathers in a general one-dimensional
chain are analysed for two particular examples of soft (Morse) and
hard (quartic) on-site potentials. The existence of discrete
breathers in one-dimensional and two-dimensional Morse lattices is
proved by using rotating wave approximation, local anharmonic
approximation and a numerical method. The localization and amplitude
of discrete breathers in the two-dimensional Morse lattice with on-site
harmonic potentials correlate closely to the Morse parameter a and
the on-site parameter к. 相似文献