共查询到19条相似文献,搜索用时 265 毫秒
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本文通过第一性原理计算(密度泛函理论结合均匀形变方法)得到过渡金属铝化物FeAl和CoAl的二阶和三阶弹性常数,这些弹性常数是通过拟合计算出的能量与应力关系得到的。计算结果和理论数据及实验值符合的很好。接下来本文又研究了FeAl和CoAl在不同压强下的弹性性质。不同压强下的弹性常数Cij,体模量B,剪切模量G,泊松比σ 也成功的得到了。B/G比值和柯西压强 PC 都表明在零压下FeAl和CoAl表现出脆性。在压强小于60GPa的情况下,增大压强可以增强它们的韧性,但它们始终表现为脆性。 相似文献
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利用全势线性muffin-tin轨道(FP-LMTO)方法, 结合在密度泛函理论框架下的广义梯度近似, 研究了六角密堆积结构超导体MgB2的晶格参数, 弹性常数, 以及体积模量及其对压强的微分. 计算结果显示当晶格参数c和a的比率c/a大约为1.138时, MgB2的结构最稳定.本文所得到的计算结果与实验值及其他作者利用不同方法得到的计算值相符合. 相似文献
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利用第一性原理平面波赝势密度泛函理论研究TiO2的结构,其零温零压下的晶格常数和常温下的体弹模量及其对压强的一阶导数的计算结果与实验值和其他理论计算结果相符.通过准谐德拜模型,获得了相对晶格常数、相对体积、体弹模量、热膨胀系数、热容与温度和压强的关系. 相似文献
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基于密度泛函理论的第一性原理计算获得了α-Ti2Zr的晶体结构、弹性常数、德拜温度和电子分布情况, 研究了它们与压力的关系. 计算得到的晶体结构参数与实验值一致. 运用有限应变方法计算得到了α-Ti2Zr的体积模量B、剪切模量G、杨氏模量E和泊松比σ. B和E的零压值分别为101.2和35.6 GPa. G/B的值较小, 并且随着压力的增加而减小, 表明α-Ti2Zr具有优异的延展性. 基于弹性常数得到平均声速, 从而获得了德拜温度Θ=321.7 K. 通过解Christoffel方程获得的压缩波和剪切波数据揭示α-Ti2Zr具有较强的各向异性. 此外, 压力诱导电子从s轨道到d轨道的转移说明在一定压力下α-Ti2Zr将转变为β相.
关键词:
第一性原理
α-Ti2Zr')" href="#">α-Ti2Zr
物性
高压 相似文献
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AlB2弹性常数的第一性原理计算 总被引:1,自引:1,他引:0
利用基于局域密度近似框架下的第一原理平面波赝势方法,结合HGH型相对论分析赝势,对AlB2的晶格参数和弹性常数进行了计算.结果显示:当晶格参数c和a的比率c/a为1.084时,具有最稳定的几何结构,与实验值及其他理论得到的计算值相符合. 相似文献
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The second and third order elastic constants of the alkali metals have been calculated on the long wave method using the Heine-Abarenkov lacal model potential with different exchange-correlation corrections. It is found that the use of an exchange correlation correction which satisfies the compressibility sum rule leads to a good agreement between the calculated and measured second order elastic constants of the alkali metals Na, K, Rb and Cs. The shear elastic constants however come out correct even if the compressibility sum rule is violated by the exchange-correlation correction. The third order elastic constants and the pressure derivatives of the second order elastic constants and the pressure derivatives of the second order elastic constants calculated on the HA local potential are lower than the experimental values at room temperature. The discrepancy is pronounced for the heavier alkali metals. Similar calculations using the Wallace potential for Li, Na and K and the Schneider-Stoll potential for Rb give the pressure derivative in good agreement with experiment. In view of the important role by the exchange correlation correction, Suzuki's results calculated without taking this correction into account can only be accepted with some reservation. 相似文献
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G.R. Barsch 《Solid State Communications》1974,14(10):983-987
Relations for the third and fourth order elastic constants are derived from a Landau-Devonshire type free energy function for crystals with the A15 structure which undergo the structural transformation at low temperature. Application to transforming V3Si at 21° K gives in connection with experimental data for the pressure derivatives of the elastic constants unusually large numerical values for c111, c112, c123 and c1111. The stress-' strain relation calculated from these data is in semiquantitative agreement with the directly measured, strongly non-linear behavior. 相似文献
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C.S. MenonR. Ramji Rao 《Journal of Physics and Chemistry of Solids》1972,33(6):1325-1334
The lattice dynamics and the anharmonic properties of the hexagonal Zirconium are worked out using Keating's approach. The dispersion curves are fitted using twelve second order parameters and the six second order elastic constants are evaluated. The ten third order elastic constants are calculated using five third order parameters. The experimental measurements on the pressure derivatives of the second order elastic constants in Zirconium are in good agreement with the calculated values. The low-temperature limit of the lattice thermal expansion is calculated which agrees well with the value obtained from thermal expansion data. The variation of the generalised GPs of the elastic modes with the direction of propagation is illustrated by polar diagram. 相似文献
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Elastic constants and thermodynamic properties of Mg2SixSn1-x from first-principles calculations 下载免费PDF全文
<正>This paper stuides the elastic constants and some thermodynamic properties of Mg2SixSnn-1(x=0,0.25,0.5, 0.75,1) compounds by first-principles total energy calculations using the pseudo-potential plane-waves approach based on density functional theory,within the generalized gradient approximation for the exchange and correlation potential. The elastic constants of Mg2SixSnn-1 were calculated.It shows that,at 273 K,the elastic constants of Mg2Si and Mg2Sn are well consistent with previous experimental data.The isotropy decreases with increasing Sn content.The dependences of the elastic constants,the bulk modulus,the shear modulus and the Debye temperatures of Mg2Si and Mg2Si0.5Sn0.5 on pressure were discussed.Through the quasi-harmonic Debye model,in which phononic effects were considered,the specific heat capacities of Mg2SixSn1-x at constant volume and constant pressure were calculated.The calculated specific heat capacities are well consistent with the previous experimental data. 相似文献
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General expressions have been derived for the second order elastic constants and third order elastic constants of the A-15 structure compounds with the nearest neighbour central interaction. The second order elastic constants, the third order elastic constants and the pressure derivatives of the second order elastic constants of V3Si and V3Ge are reported and compared with the available experimental measurements. 相似文献
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The lattice dynamics, second and third order elastic constants and the lattice thermal expansion of dysprosium have been calculated using Keating's approach. The ten third order elastic constants are calculated using four anharmonic parameters. The present model reproduces the measured pressure derivatives of the second order elastic constants of dysprosium well. The low and high temperature limits γ?I and γ?H of the lattice thermal expansion are evaluated and the agreement between the calculated γ?H and that obtained from the thermal expansion and specific heat data is satisfactory. 相似文献
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Yifang Ouyang Xiaoma Tao Hongmei Chen Yuanping Feng 《Physica B: Condensed Matter》2009,404(16):2299-2304
The elastic constants of the Al, Mg and rare earth (RE) lanthanide elements have been calculated at T=0 K by using the projector augmented-wave (PAW) method within the generalized gradient approximation (GGA). The bulk moduli, shear moduli, Young's moduli and Poisson's ratio of poly-crystalline solid are estimated from the calculated elastic constants of single crystal. Based on the quasi-harmonic Debye model, the Debye temperature, heat capacity, Grüneisen parameter and linear thermal expansion coefficient are also estimated. The present calculated results are in reasonable agreement with the available experimental data and other theoretical results. The present calculation of elastic constants for Ce also indicates that the PAW potential (named “Ce_3”), for which one f electron is kept frozen in the core and hence fix the valency of Ce to three (Ce_3) does not yield good results for the elastic constants. 相似文献
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A systematic investigation of the lattice dynamics, second and third order elastic constants and the temperature variation of the effective Grüneisen functions has been carried out in gadolinium using Keating's approach. The ten third order elastic constants are calculated using five anharmonic parameters. The present model reproduces the measured pressure derivatives of the second order elastic constants of gadolinium well. The low and high temperature limits ggL and ggH of the lattice thermal expansion are evaluated. The agreement between the calculated ggH and that obtained from the thermal expansion and specific heat data of gadolinium is good. 相似文献
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Yifang Ouyang Xiaofeng Tong Chang Li Hongmei Chen Xiaoma Tao Tilmann Hickel Yong Du 《Physica B: Condensed Matter》2012,407(23):4530-4536
With this work we present a newly developed potential for the Fe–Al system, which is based on the analytical embedded atom method (EAM) with long range atomic interactions. The potential yields for the two most relevant phases B2-FeAl and D03-Fe3Al lattice constants, elastic constants, as well as bulk and point defect formation enthalpies, which are in good agreement with experimental and other theoretical data. In addition, the phonon dispersions for B2-FeAl and D03-Fe3Al show a good agreement with available experiments. The calculated lattice constants and formation enthalpy for disordered Fe–Al alloys are in good agreement with experimental data or other theoretical calculations. This indicates that the present EAM potentials of Fe–Al system is suitable for atomistic simulations of structural and kinetic properties for the Fe–Al system. 相似文献