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1.
通过用中子非弹性散射测量旋声晶体高对称方向的横声学支声子色散曲线的劈裂,从三个方面研究了同构异质晶体Bi12GeO20和Bi12SiO20的旋声特性。值得注意的是,沿〈111〉方向传播的左旋、右旋圆偏振声子具有不同的衰减。其中传播速度快的圆偏振声子衰减较大,该结论为这两种晶体所证实,这是在晶体旋声性研究中首次观察到的现象。实验还直接确定了衰减较大的这支声子的寿命约为2×10-11S。 关键词:  相似文献   

2.
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   

3.
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   

4.
KIO3晶体的折射率和非线性光学性能   总被引:1,自引:0,他引:1       下载免费PDF全文
尹鑫  吕孟凯  程端平 《物理学报》1987,36(11):1492-1495
本文在可见光波长范围内测量了未极化的KIO3晶体的三个不同方向的折射率,用实验方法证实了KIO3晶体存在Ⅰ尖位相匹配曲面,找到了未极化的KIO3晶体的最佳位相匹配方向。 关键词:  相似文献   

5.
采用电弧法制备了C60/C70,并用光学显微镜、扫描电子显微镜和透射电子显微镜对其结晶形貌进行了研究。研究结果表明,C60/C70晶体依平面状长大方式生长,最终长成规则的四边形,五边形和六边形晶体。 关键词:  相似文献   

6.
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. 关键词: 3Sb2')" href="#">α-Mg3Sb2 第一性原理 电子结构 力学性能  相似文献   

7.
LaF3:Nd3+的斯塔克子能级能量值的计算   总被引:1,自引:0,他引:1       下载免费PDF全文
用C2格位对称的晶体场哈密顿量对LaF3:Nd3+进行全谱项能量值的拟合计算,单次计算的均方根误差σ约为20.2cm-1。同时,本文更正了以前对少数子能级的不正确归属。 关键词:  相似文献   

8.
YGG:Cr3+晶体的光谱特性   总被引:1,自引:0,他引:1       下载免费PDF全文
本文通过实验研究了YGG:Cr3+晶体的光谱特性,报道了室温下的吸收谱,10,133,300K的荧光谱,以及荧光寿命、无辐射跃迁几率、辐射量子效率与温度之间的依赖关系。从吸收谱及荧光谱中确定在C3i(S6)低对称场微扰下,Cr3+离子在基质YGG中2T1能级分裂的子能级及基态+A22E零声子跃迁R线的位置。 关键词:  相似文献   

9.
调谐激光晶体Cr3+:ZnWO4光致发光特性的研究   总被引:1,自引:0,他引:1       下载免费PDF全文
研究了调谐激光晶体Cr3+:ZnWO4的光致发光特性。报道了它的吸收光谱、激发光谱、发射光谱及其随温度的变化、零声子跃迁和发射寿命等实验结果,并讨论了激发特性、电子-声子耦合作用、ZnWO4中Cr3+的发射寿命曲线等相关问题。 关键词:  相似文献   

10.
刘春旭 《中国光学》2014,7(6):931-935
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   

11.
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   

12.
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   

13.
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   

14.
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   

15.
C42+的几何构型和Jahn Teller效应   总被引:1,自引:0,他引:1       下载免费PDF全文
汪蓉  朱正和  杨传路 《物理学报》2001,50(9):1675-1680
用从头计算法QCISD/6-311G得到了C42+分子的10种不同的几何构型,其中包括Cs,C∞v,C2v,D2h,D∞h,D4h,D2d,C3v等不同的构型.计算表明C42+的Td构型不能稳定存在,详细讨论了Td 关键词: 几何构型 42+')" href="#">C42+ Jahn Teller效应  相似文献   

16.
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   

17.
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   

18.
王汝菊  王积方  查济璇 《物理学报》1985,34(8):1088-1095
本文从基本的压电Christoffel方程出发导出三角晶系3m点群压电晶体弹性常数的表示式。并采用10MHz射频超声脉冲回波重合法测量了沿LiNbO3不同对称方向传播的声速,结合eij和εij5给出了LiNbO3全部弹性常数CijE和CijD。它们是C11E=19.8 关键词:  相似文献   

19.
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 C3F-C3vT-C3vT?. The following nonzero potential coefficients were obtained for CH3OCH3: V30 = V03 = 909.05 ± 0.49 cm?1, V33 = 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   

20.
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   

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