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The accurate prediction of the electronic properties of materials at a low computational expense is a necessary condition for the development of effective high-throughput quantum-mechanics (HTQM) frameworks for accelerated materials discovery. HTQM infrastructures rely on the predictive capability of density functional theory (DFT), the method of choice for the first-principles study of materials properties. However, DFT suffers from approximations that result in a somewhat inaccurate description of the electronic band structure of semiconductors and insulators. In this article, we introduce ACBN0, a pseudohybrid Hubbard density functional that yields an improved prediction of the band structure of insulators such as transition-metal oxides, as shown for TiO 2 , MnO, NiO, and ZnO, with only a negligible increase in computational cost.

Employing ab initio electronic structure calculations, we predict that trigonal tellurium consisting of weakly interacting helical chains undergoes a trivial insulator to strong topological insulator (metal) transition under shear (hydrostatic or uniaxial) strain. The transition is demonstrated by examining the strain evolution of the band structure, the topological Z 2 invariant and the concomitant band inversion. The underlying mechanism is the depopulation of the lone-pair orbitals associated with the valence band via proper strain engineering. Thus, Te becomes the prototype of a novel family of chiral-based three-dimensional topological insulators with important implications in spintronics, magneto-optics, and thermoelectrics. DOI: 10.1103/PhysRevLett.110.176401 PACS numbers: 71.15.Ap, 72.25.Dc, 73.20.At, 73.43.Nq The recent discovery of three-dimensional (3D) topological insulators (TIs) has sparked intense efforts in the search for novel materials that exhibit this new quantum-mechanical state of matter driven by strong spin-orbit coupling, which leads to the appearance of spin-momentum-locked topologically protected surface states with a Dirac-cone energy dispersion [1][2][3]. Ongoing research efforts focus primarily on the prototypical family of Bi 2 Te 3 , Bi 2 Se 3 , and Sb 2 Te 3 3D TIs, which exhibit a quintuple layered structure along the c axis of the hexagonal lattice. The intra-and interlayer coupling within one quintuple layer is covalentlike while the interaction between two quintuple layers is much weaker, predominantly of the van der Waals type [3][4][5].The heavier group-VI elements selenium and tellurium are ubiquitous in most of the recently discovered binary or ternary TIs and exhibit a wide variety of interesting properties under pressure. They undergo complex structural changes [6], exhibit semiconductor-to-metal transitions [7], have unusual melting curves [8], and some of their high-pressure phases are superconducting at low temperatures [6]. At ambient conditions, tellurium has a trigonal crystal structure (Te-I) with space group D 4 3 consisting of weakly interacting infinite helical chains arranged in a hexagonal array, which spiral around axes parallel to c. The unit cell shown in Fig. 1(a) has three atoms at the positions (u, 0, 0), (0, u, 1=3), and ( " u, " u, 2=3) in units of the lattice vectors [9], where u is the internal atomic position parameter. Each atom forms strong covalentlike intrachain bonds with its two nearest neighbors (NNs) and weak van der Waals-like interchain bonds with its four next NNs, with bond lengths of r ¼ 2:91 # A and R ¼ 3:43 # A, respectively. This unique feature is reflected in liquid-state studies of Te which showed that the chain structure is retained above the melting temperature [8].In this Letter we predict that Te-I, a noncentrosymmetric material, becomes a strong TI or topological metal (TM) under application of shear or uniform and uniaxial strain, respectively. In most reported TIs to date, the band inversion and the gap closing occur n...