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用中子相干非弹性散射、沿三个主晶轴方向测量了同构异质晶体NaBrO_3和NaClO_3的声子色散关系。从小波矢区的实验结果获得了沿晶体这些方向的弹性波速及三个独立的弹性常数C_(11),C_(12),C_(44)。实验结果表明,尽管这两种晶体在旋声方面表现出十分不同的特性,但是,它们的左旋和右旋圆偏振声子的声速都是在一个特定的平均速度v_(T_D)上下均衡的分布,这个平均速度可由其它方向的弹性波速或零级近似的弹性常数唯一确定。即Portigal理论的这一预言获得了实验上的明确证据。 相似文献
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从声子-电磁激元频率色散关系的普遍公式出发,推导出了单轴晶体的Merten方程和电磁激元的频率色散关系。测量了BaTiO3和Ce:BaTiO3晶体的简正模和斜声子的喇曼散射谱,并根据Merten方程,拟合出了斜声子的方向色散曲线;记录了A1类电磁激元在不同波矢值下的喇曼谱,观察到其频率色散现象.根据以上结果,对A1(TO)模喇曼谱中两个宽的非对称峰的归属和BaTiO3晶体的结构相变机制进行了讨论;计算出了这两种晶体的受夹介电常数;分析了掺Ce对BaTiO3晶体结构的影响。
关键词: 相似文献
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运用第一性原理研究了Mg-Sb合金中典型沉淀相α-Mg3Sb2的几何、电子结构和力学性能.结构优化得到的晶格常数和形成能与实验值符合很好.电子结构分析表明,具有半导体性质的α-Mg3Sb2带隙为0.303 eV,是间接带隙半导体.通过计算得到了α-Mg3Sb2的弹性常数,进而得到模量、泊松比等力学参数,对力学参数进行分析发现,α-Mg3Sb2有很好的延展性而塑性相对较差.通过对α-Mg3Sb2施加应变前后态密度的变化分析,发现对于六角结构的α-Mg3Sb2,与剪切模量相关的C11+C12,C33/2和与体模量相关的C11+C12+2C13+C33/2对体积变化不保守,而(C11-C12)/4和C44对体积变化保守.
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3Sb2')" href="#">α-Mg3Sb2
第一性原理
电子结构
力学性能 相似文献
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采用燃烧法合成了La1.6(MoO4)3:Eu0.43+纳米晶末,研究了其声子-掺杂-晶格相互作用和发光性质.X射线粉末衍射(XRD)分析表明,在500~900 ℃退火后,La1.6(MoO4)3:Eu0.43+样品为单一晶相.对样品进行了光致发光(PL)测量,激发Mo6+-O2-电荷迁移带,观察到Eu3+的系列发光,表明Mo6+-O2-带和Eu3+间存在能量传递,中心波长分别在λ1=469 nm和λ2=426 nm处的两个one-phonon边带,相应的声子能量分别为767和1202 cm-1,分别对应于 Mo=O 和Mo-O-Mo伸缩振动.同时,计算了两个局域模电子-声子耦合强度的黄昆因子分别为S1=0.055和S2=0.037,为揭示其三价离子高传导特性及其负热膨胀物理特性提供了实验基础. 相似文献
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The initial slopes of the acoustic phonon dispersion curves in (V0.98Cr0.02)2O3 have been measured at room temperature in several of the high symmetry directions by inelastic neutron scattering. From these data several sound velocities and four independent elastic constants have been determined. Although the Cr doped specimen is in the insulating phase and pure V2O3 is metallic, these results are in good agreement with recent data (1) obtained by ultrasonic measurements on pure V2O3. 相似文献
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The acoustic phonon dispersion curves for CoCl2 have been measured, in the three principal symmetry directions, by inelastic neutron scattering at room temperature. From the initial slopes the sound velocities have been derived and the elastic constants calculated. The two dimensional nature of the structure of CoCl2 is apparent in the difference between the sound velocities parallel and perpendicular to the closed packed layers. 相似文献
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Acoustic phonon dispersion curves have been determined by inelastic neutron scattering in the intermetallic compound SrGa2. This compound crystallizes in the AlB2 type of structure which contains alternating planar Sr and Ga layers normal to the c-axis. The dispersion of the acoustic modes of the three principal directions revealed no strong two dimensional character in terms of sound velocities and elastic constants. 相似文献
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Neutron measurements of the dispersion curve v(q) for [10·0] phonons polarized in [11·0] are presented for hexagonal close-packed Zr at 300°, 773°, and 1073°K. Given that the crystal transforms to b.c.c. at 1135°K and demonstrates a pronounced softening in the C66 elastic constant, v(q) shows only a uniform lowering of the entire branch, consistent with the behavior of C66(T) but fractionally smaller for large wave vectors. No anomalous phonon linewidths are observed. 相似文献
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Multiple crossings of Lamb modes found in [001]c and [011]c polarized (1−x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-xPT, x=0.33 and 0.29, respectively) plates have been studied by comparing their slowness patterns with their dispersion patterns. Multiple bandgaps and crossings of Lamb wave dispersion curves are directly related to the multivalued curves in region II, and a pair of complex conjugate b2 values in region I of their slowness curves. An expression composed of elastic and piezoelectric constants has been derived to judge whether S0 and A0 modes cross with each other. This expression can be greatly simplified for non-piezoelectric materials, and there are no crossings of Lamb modes for isotropic materials. 相似文献
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Cihan Parlak 《Physica B: Condensed Matter》2012,407(13):2622-2625
We report a detailed ab initio study of the structural, electronic, and volume dependent elastic and lattice dynamical properties of Sr(Ni0.5Si0.5)2. The calculations have been carried out within the local density functional approximation using norm-conserving pseudopotentials and a plane-wave basis. The phonon dispersion curves along the high-symmetry directions and phonon frequencies with their Grüneisen parameters at the Brillouin zone center are computed by using density functional perturbation theory while the elastic constants are calculated in metric-tensor formulation. The band structure, and partial densities of states and Fermi surface topology are also discussed. 相似文献
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The multiplet splitting patterns of microwave transitions in the ground state and the first two torsional excited states of CH3OCH3, CD3OCD3, and CD3OCH3 were analyzed in terms of the semirigid rotor models C2vF-C3vT-C3vT and . The following nonzero potential coefficients were obtained for CH3OCH3: V30 = V03 = 909.05 ± 0.49 cm?1, V′33 = 5.06 ± 1.60 cm?1; for CD3OCH3: V30(CD3) = 897.18 ± 2.41 cm?1, V03(CH3) = 910.45 ± 0.33 cm?1; for CD3OCD3: V30 = V03 = 897.00 cm?1. These results are compared to earlier microwave studies of these molecules. 相似文献
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Longitudinal and transverse phonon frequencies in superionic (AgI)x(AgPO3)1?x glasses for x = 0.3, 0.4 and 0.5 have been measured by Brillouin scattering. The hypersonic velocities as a function of temperature were determined along with the elastic constants. The velocity data extrapolate linearly to those of α-AgI in support of a local cluster model. 相似文献