排序方式: 共有18条查询结果,搜索用时 15 毫秒
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基于第一性原理计算,这篇文章研究了单壁锯齿型和扶手型石墨炔管的几何结构、电子结构以及杨氏模量.计算表明:石墨炔管是一类具有一定能隙的直接带隙半导体管,其带隙在0.4-1.3eV的能量范围,且随管径的增大而变小.而石墨炔管的杨氏模量在0.44-0.50Tpa区间变化.对于锯齿型石墨炔管,其杨氏模量随着半径的增大而变小而锯齿型石墨炔管的杨氏模量随其半径的增大而增大. 相似文献
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Based on a force constant model, we investigated the phonon spectrum and then specific heat of single-walled boron nitride nanotubes. The results show that the frequencies of Raman and infrared active modes decrease with increasing diameter in the low frequency, which is consistent with the results calculated by density functional theory. The fitting formulae for diameter and chirality dependence of specific heat at 300K are given. 相似文献
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为了探求过渡金属催化剂对催化合成储氢材料NaAlH4效果的影响, 本文采用第一性原理方法研究了多种金属原子取代Al (111)表面铝原子形成的合金表面对氢的催化分解的影响. 计算结果表明, Sc, V, Fe, Ti原子掺杂的表面对氢分子分解具有催化作用. H2在对应的掺杂表面催化分解所需要的活化能分别为0.54 eV, 0.29 eV, 0.51 eV, 0.12 eV. H原子在Sc, V, Ti掺杂表面扩散需要的活化能分别为0.51 eV, 0.66 eV, 0.57 eV. 同时, 过渡金属掺杂在Al表面时倾向于分散分布, 增加掺杂表面的掺杂原子个数, 掺杂表面的催化效果体现为单个掺杂过渡金属原子的催化效果. 本研究将为金属掺杂Al (111)表面催化加氢合成NaAlH4提供理论参考. 相似文献
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基于密度泛函理论的第一性原理并结合非平衡格林函数, 探讨了应变对 BaTiO3 铁电薄膜漏电流的影响规律.研究表明,压应变能有效地抑制BaTiO3 铁电薄膜漏电流, 特别是当压应变为4%时,其漏电流相对无应变状态降低了近10 倍.通过考察体系的透射系数和电子态密度发现: 一方面压应变状态下铁电隧道结的透射几率要比张应变时小,特别是在费米面附近;另一方面随着张应变过渡至压应变时,价带的位置逐渐向低能区移动而导带向高能区移动,导致了其带隙的增大, 从而有效抑制了漏电流. 本研究为寻找抑制铁电薄膜漏电流,提高铁电薄膜及铁电存储器的性能提供合适的方法.
关键词:
铁电薄膜
双轴应变
漏电流
第一性原理 相似文献
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We calculate the vibrational properties of potassium-doped single-walled carbon nanotubes within lattice dynamical theory. The results show that the frequency of high-frequency Raman mode E29 for K5C40 downshifts to 1553cm^-1, which is in agreement with the value for highly doped samples with effective composition KC8.Moreover, the specific heat curves have a turnover at 22 K, originating from the saturation of K atoms vibrational modes at low energy. 相似文献
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We have calculated the differential conductance of metallic carbon nanotubes by the scatter matrix methon.It is found that the differential conductance of metallic nanotube-based devices oscillates as a function of the bias voltage between the two leads and the gate voltage.Oscillation period T is directly proportional to the reciprocal of nanotube length.In addition,we found that electronic transport properties are sensitive to variation of the length of the nanotube. 相似文献
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The thermal conductivity of GaAs/AlAs superlattices limited by the three-phonon Umklapp process and boundary scattering has been studied theoretically based on the model of lattice dynamics with force constant matrix. It was found that the Umklapp relaxation rate approximates BTω^2/n with a fitting parameter B. The thermal conductivity increases with the increase of temperature at low temperatures, and would show a peak behaviour at about 60K before falling off at high temperatures. In addition, the thermal conductivity increases with the increase of period thickness of the superlattices. 相似文献