镓基液态金属的结构与物性

镓基液态金属由于其良好的流动性以及高导电导热性,在室温范围内展现出许多与固态金属材料不同的性质,也突破了固态金属无法实现的一些瓶颈,在柔性器件、软体机器人等方面展现巨大的应用前景。镓基液态金属的特殊物性与其原子结构、键价关系、电子性质等密切关联。深入理解镓基液态金属的基本结构与物性,对研究和应用液态金属材料有着重要意义。文章从液态金属的微观原子结构着手,综述了研究液态金属基本物性的常用理论和分析方法,并以此剖析了镓基液态金属最引人关注的一些性质,最后对液态金属物性研究及扩展其应用领域的可能方向进行了探讨。

Electronic structure of cuprate-nickelate infinite-layer heterostructure

The discovery of superconductivity in Sr/Ca-doped infinite-layer nickelates Nd(La)NiO_(2)thin films inspired extensive experimental and theoretical research.However,research on the possibilities of enhanced critical temperature by interface heterostructure is still lacking.Due to the similarities of the crystal structure and band structure of infinite-layer nickelate La NiO_(2)and cuprate CaCuO_(2),we investigate the crystal,electronic and magnetic properties of La NiO_(2):CaCuO_(2)heterostructure using density functional theory and dynamical mean-field theory.Our theoretical results demonstrate that,even a very weak inter-layer z-direction bond is formed,an intrinsic charge transfer between Cu-3d_(x^(2)-y^(2))and Ni-3d_((x^(2)-y^(2)))orbitals is obtained.The weak interlayer hopping between Cu and Ni leaves a parallel band contributed by Ni/Cu-3d_((x^(2)-y^(2)))orbitals near the Fermi energy.Such an infinite-layer heterostructure with negligible interlayer interaction and robust charge transfer opens a new way for interface engineering and nickelate superconductors.

浅谈导师制对本科生独立人格和创新能力的培养

文章对独立人格的基本概念及培养现状进行了分析,指出了本科生人格培养过程中存在的问题,从优势、实施思路及实施原则三个角度阐述了本科生导师制的基本内涵,提出了基于本科生导师制培养学生自我建设精神、怀疑精神和创新精神,造就具有独立人格创新型人才的具体策略。

应变下氮和硼替位掺杂石墨烯的结构与电子性质

采用第一性原理计算方法,研究了氮(N)和硼(B)替位掺杂石墨烯在加载应变情况下的结构和电子性质.计算结果表明(采用6×6超原胞),对于纯石墨烯,当应变大于临界应变30%时发生从弹性应变至非弹性应变的转变,体系总能在转变处发生突变.而N和B掺杂石墨烯的临界应变分别变为17.6%和17.4%,这表明掺杂石墨烯的弹性应变范围大幅减小.通过研究纯石墨烯和N/B替位掺杂石墨烯的电子性质,发现纯石墨烯在对称应变下仍为零带隙,而掺杂后费米能级处出现电子态,体系转变为金属,并且发现应变可以调节掺杂石墨烯的费米能级但不能在狄拉克锥处打开带隙.

Excellent thermoelectric performance predicted in Sb_(2)Te with natural superlattice structure

Using first-principles calculations combined with the Boltzmann transport theory,we explore the thermoelectric properties of natural superlattice(SL)structure Sb_(2)Te.The results show that n-type Sb_(2)Te possesses larger Seebeck coefficient of 249.59(318.87)μV/K than p-type Sb_(2)Te of 219.85(210.38)μV/K and low lattice thermal conductivity of 1.25(0.21)W/mK along the in-plane(out-of-plane)direction at 300 K.The excellent electron transport performance is mainly attributed to steeper density of state around the bottom of conduction band.The ultralow lattice thermal conductivity of Sb_(2)Te is mainly caused by low phonon group velocity and strong anharmonicity.Further analysis shows that the decrease of group velocity comes from flatter dispersion curves which are contributed by the Brillouin-zone folding.The strong anharmonicity is mainly due to the presence of lone-pair electrons in Sb_(2)Te.Combining such a high Seebeck coefficient with the low lattice thermal conductivity,maximum n-type thermoelectric figure of merit(ZT)of 1.46 and 1.38 could be achieved along the in-plane and out-of-plane directions at room temperature,which is higher than the reported values of Sb_(2)Te_(3).The findings presented here provide insight into the transport property of Sb_(2)Te and highlight potential applications of thermoelectric materials at room temperature.

Thermoelectric properties of orthorhombic silicon allotrope Si(oP32)from first-principles calculations

The diamond-like cubic silicon(d-Si)is widely used in modern electronics and solar cell industries.However,it is not an optimal candidate for thermoelectric application due to its high lattice thermal conductivity.Si(oP32)is a recently predicted orthorhombic silicon allotrope,whose total energy is close to that of d-Si.Using first-principles calculations and Boltzmann transport theory,we systematically investigate the thermoelectric properties of Si(oP32).The lower phonon thermal conductivity and higher power factor are obtained in Si(oP32)than those in diamond silicon.The low phonon thermal conductivity(33.77 W/mK at 300 K)is mainly due to the reduction of the phonon group velocity and enhancement of phonon-phonon scattering(including scattering phase space and strength).Meanwhile,the results also show that the thermoelectric performance along the zz lattice direction is better than that along the xx and yy lattice directions,and the figure of merit(700 K)along the zz lattice direction could approach to 2.45 and 1.75 for p-type and n-type Si(oP32),respectively.The values are much higher than those of d-Si(about 0.06))and Si24(0.6),indicating that the Si(oP32)is a promising candidate for thermoelectric applications.Our theoretical studies shed light on the thermoelectric properties of Si(oP32)and could stimulate further experimental studies.

硅晶体表面石墨烯褶皱形貌的分子动力学模拟研究

本文利用分子动力学的方法和模拟退火技术从原子尺度分析研究了Si(100),Si(111)和Si(211)表面单原子层石墨烯的褶皱形貌及其演化特点.研究表明,分别置于Si晶体的三种不同原子表面的石墨烯都展现出原子尺度的褶皱形貌.石墨烯与Si晶体表面原子的晶格失配是引起石墨烯褶皱的主要原因.研究发现,Si晶体表面石墨烯的褶皱形貌强烈的依赖于退火温度.石墨烯的褶皱形貌还将直接影响其在Si晶体表面的吸附稳定性.这些研究结果有助于人们认识基于Si晶体衬底的石墨烯的结构形貌及其稳定性,为石墨烯的进一步应用提供理论参考.