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3.0

Jun 30, 2018
06/18

by
Xiyue Cheng; Ronghan Li; Xing-Qiu Chen; Dianzhong Li; Yiyi Li

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By means of first-principles calculations, we found that the early characterized three-dimensional topological bulk Dirac semimetal of the $P$6$_3$/$mmc$ Na$_3$Bi is dynamically unstable at the ground state due to the presence of the large imaginary phonon frequencies around the $K$ point. Alternatively, our calculations suggest a new ground state phase which crystalizes in the $P$$\overline3$$c$1 structure with a buckled graphite-like Na/Bi sheets, which is both energetically and dynamically...

Topics: Materials Science, Condensed Matter

Source: http://arxiv.org/abs/1404.1157

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2.0

Jun 30, 2018
06/18

by
Xing-Qiu Chen; Ronghan Li; Yan Sun; Xiyue Cheng; Dianzhong Li; Yiyi Li

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By means of first-principles and \emph{ab initio} tight-binding calculations, we found that the compound of NaBi is a three-dimensional non-trivial topological metal. Its topological feature can be confirmed by the presence of band inversion, the derived effective Z$_2$ invariant and the non-trivial surface states with the presence of Dirac cones. Interestingly, our calculations further demonstrated that NaBi exhibits the uniquely combined properties between the electron-phonon coupling...

Topics: Materials Science, Condensed Matter

Source: http://arxiv.org/abs/1408.0491

2
2.0

Jun 29, 2018
06/18

by
Ronghan Li; Xiyue Cheng; Hui Ma; Shoulong Wang; Dianzhong Li; Zhenyu Zhang; Yiyi Li; Xing-Qiu Chen

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Beryllium is a simple alkali earth metal, but has been the target of intensive studies for decades because of its unusual electron behaviors at surfaces. Puzzling aspects include (i) severe deviations from the description of the nearly free electron picture, (ii) anomalously large electron-phonon coupling effect, and (iii) giant Friedal oscillations. The underlying origins for such anomalous surface electron behaviors have been under active debate, but with no consensus. Here, by means of...

Topics: Materials Science, Condensed Matter

Source: http://arxiv.org/abs/1603.03974

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3.0

Jun 29, 2018
06/18

by
Ronghan Li; Yuanfeng Xu; Jianggang He; Sami Ullah; Jiangxiu Li; Jun-Ming Liu; Dianzhong Li; Cesare Franchini; Hongming Weng; Xing-Qiu Chen

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The recent discoveries of ferroelectric metal and Weyl semimetal (WSM) have stimulated a natural question: whether these two exotic states of matter can coexist in a single material or not. These two discoveries ensure us that physically it is possible since both of them share the same necessary condition, the broken inversion symmetry. Here, by using first-principles calculations, we demonstrate that the experimentally synthesized nonmagnetic HgPbO$_3$ represents a unique example of such...

Topics: Materials Science, Condensed Matter

Source: http://arxiv.org/abs/1610.07142

2
2.0

Jun 30, 2018
06/18

by
Peitao Liu; Weiwei Xing; Xiyue Cheng; Dianzhong Li; Yiyi Li; Xing-Qiu Chen

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By means of first-principles calculations coupled with the kinetic Monte Carlo simulations, we have systematically investigated the effects of dilute substitutional solutes on the behaviors of carbon in $\alpha$-Fe. Our results uncover that: ($i$) Without the Fe vacancy the interactions between most solutes and carbon are repulsive due to the strain relief, whereas Mn has a weak attractive interaction with its nearest-neighbor carbon due to the local ferromagnetic coupling effect. ($ii$) The...

Topics: Materials Science, Condensed Matter

Source: http://arxiv.org/abs/1407.2993

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4.0

Jun 30, 2018
06/18

by
Jiangxu Li; Hui Ma; Shaobo Feng; Sami Ullah; Ronghan Li; Junhua Dong; Dianzhong Li; Yiyi Li; Xing-Qiu Chen

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Topological nodal line (DNL) semimetals, formed by a closed loop of the inverted bands in the bulk, result in the nearly flat drumhead-like surface states with a high electronic density near the Fermi level. The high catalytic active sites associated with the high electronic densities, the good carrier mobility, and the proper thermodynamic stabilities with $\Delta G_{H^*}$$\approx$0 are currently the prerequisites to seek the alternative candidates to precious platinum for catalyzing...

Topics: Materials Science, Condensed Matter

Source: http://arxiv.org/abs/1704.07043

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Sep 23, 2013
09/13

by
Yan Sun; Xing-Qiu Chen; Dianzhong Li; Cesare Franchini; Seiji Yunoki; Yiyi Li; Zhong Fang

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We explore the topological behavior of the binary Zintl phase of the alkaline earth metals based compounds Sr$_2$Pb and Sr$_2$Sn using both standard and hybrid density functional theory. It is found that Sr$_2$Pb lies on the verge of a topological instability which can be suitably tuned through the application of a small uniaxial expansion strain ($>$ 3%). The resulting non-trivial topologically insulating state display well-defined metallic states in the Sr$_{2}$Pb(010) surface, whose...

Source: http://arxiv.org/abs/1105.5841v1

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Jun 27, 2018
06/18

by
Peitao Liu; Sergii Khmelevskyi; Bongjae Kim; Martijn Marsman; Dianzhong Li; Xing-Qiu Chen; D. D. Sarma; Georg Kresse; Cesare Franchini

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We put forward a scheme to study the anisotropic magnetic couplings in Sr2IrO4 by mapping fully relativistic constrained noncollinear density functional theory including an on-site Hubbard U correction onto a general spin model Hamiltonian. This procedure allows for the simultaneous account and direct control of the lattice, spin and orbital interactions within a fully ab initio scheme. We compute the isotropic, single site anisotropy and Dzyaloshinskii-Moriya (DM) coupling parameters, and...

Topics: Condensed Matter, Strongly Correlated Electrons

Source: http://arxiv.org/abs/1503.06753

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Jun 27, 2018
06/18

by
Xiyue Cheng; Ronghan Li; Dianzhong Li; Yiyi Li; Xing-Qiu Chen

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By means of first-principles calculations, we identified the structural phase transition of Na$_3$Bi from hexagonal ground state to cubic $cF$16 phase above 0.8 GPa, in agreement with the experimental findings. Upon the releasing of pressure, \emph{cF}16 phase of Na$_3$Bi is mechanically stable at ambient condition. The calculations revealed that the $cF$16 phase is topological semimetal, in similarity to well-known HgTe and it even exhibits an unusually low $C^\prime$ modulus (only about 1.9...

Topics: Condensed Matter, Materials Science

Source: http://arxiv.org/abs/1505.03936

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Sep 21, 2013
09/13

by
Xing-Qiu Chen; Haiyang Niu; Cesare Franchini; Dianzhong Li; Yiyi Li

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We revisit and interpret the mechanical properties of the recently proposed allotrope of carbon, T-carbon [Sheng \emph{et al.}, Phys. Rev. Lett., \textbf{106}, 155703 (2011)], using density functional theory in combination with different empirical hardness models. In contrast with the early estimation based on the Gao's model, which attributes to T-carbon an high Vickers hardness of 61 GPa comparable to that of superhard cubic boron nitride (\emph{c}-BN), we find that T-carbon is not a...

Source: http://arxiv.org/abs/1108.2570v1

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Jul 20, 2013
07/13

by
Haiyang Niu; Jiaqi Wang; Xing-Qiu Chen; Dianzhong Li; Yiyi Li; Petr Lazar; Raimund Podloucky; Aleksey N. Kolmogorov

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By electron and X-ray diffraction we establish that the CrB$_4$ compound discovered over 40 years ago crystallizes in the $oP10$ (\emph{Pnnm}) structure, in disagreement with previous experiments but in agreement with a recent first-principles prediction. The 3D boron network in the new structure is a distorted version of the rigid carbon $sp^3$ network proposed recently for the high-pressure C$_4$ allotrope. According to our density functional theory calculations and the analysis of the...

Source: http://arxiv.org/abs/1203.6470v1

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Jul 20, 2013
07/13

by
Haiyang Niu; Xing-Qiu Chen; Shibing Wang; Dianzhong Li; Wendy L. Mao; Yiyi Li

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We report a general scheme to systematically construct two classes of structural families of superhard sp3 carbon allotropes of cold compressed graphite through the topological analysis of odd 5+7 or even 4+8 membered carbon rings stemmed from the stacking of zigzag and armchair chains. Our results show that the previously proposed M, bct-C4, W and Z allotropes belong to our currently proposed families and that depending on the topological arrangement of the native carbon rings numerous other...

Source: http://arxiv.org/abs/1203.2998v1

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Sep 18, 2013
09/13

by
Xing-Qiu Chen; Haiyang Niu; Dianzhong Li; Yiyi Li

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Though extensively studied, hardness, defined as the resistance of a material to deformation, still remains a challenging issue for a formal theoretical description due to its inherent mechanical complexity. The widely applied Teter's empirical correlation between hardness and shear modulus has been considered to be not always valid for a large variety of materials. Here, inspired by the classical work on Pugh's modulus ratio, we develop a theoretical model which establishes a robust...

Source: http://arxiv.org/abs/1102.4063v1