First-principle theory calculations reveal record coordination numbers of CN = 13 in D13h La©C13+, CN = 12 in C2v Y©B6C6+, and CN = 11 in C2v Sc©B5C6 in planar species, effectively enriching the chemical structures and bonding patterns of planar hypercoordinated complexes.

We report the magneto-transport properties and the electronic structure of TmSb. TmSb exhibits extremely large transverse magnetoresistance and Shubnikov-de Haas (SdH) oscillation at low temperature and high magnetic field. Interestingly, the split of Fermi surfaces induced by the nonsymmetric spin-orbit interaction has been observed from SdH oscillation. The analysis of the angle-dependent SdH oscillation illustrates the contribution of each Fermi surface to the conductivity. The electronic structure revealed by angle-resolved photoemission spectroscopy (ARPES) and first-principles calculations demonstrates a gap at X point and the absence of band inversion. Combined with the trivial Berry phase extracted from SdH oscillation and the nearly equal concentrations of electron and hole from Hall measurements, it is suggested that TmSb is a topologically trivial semimetal and the observed XMR originates from the electron-hole compensation and high mobility.

Extensive first-principles theory calculations predict the possibility of bi-decker inverse sandwich complexes La2[B18], La2[B18]2−, and La2[B2@B18], with the B2-centered La2[B2@B18] as a tubular molecular rotor possessing the smallest core–shell structure.

Cage-like metallo-borospherenes exhibit unique structures and bonding. Inspired by the newly reported smallest spherical trihedral metallo-borospherene D 3h Ta 3 B 12 – ( 1 ), which contains two equivalent B 3 triangles interconnected by three B 2 units on the cage surface, we present herein a first-principles theory prediction of the perfect spherical tetrahedral metallo-borospherene T d Ta 4 B 18 ( 2 ), which possesses four equivalent B 3 triangles interconnected by six B atoms, with four equivalent nonacoordinate Ta centers in four η 9 -B 9 rings as integrated parts of the cage surface. As the well-defined global minimum of the neutral, Ta 4 B 18 ( 2 ) possesses four 10c-2e B 9 (π)–Ta(d σ ) and eight 10c-2e B 9 (π)–Ta(d δ ) coordination bonds evenly distributed over four Ta-centered Ta@B 9 nonagons, with the remaining 18 valence electrons in nine 22c-2e totally delocalized bonds following the 18-electron principle (1S 2 1P 6 1D 10 ) of a superatom. Such a bonding pattern renders spherical aromaticity to the tetrahedral complex, which can be used as building blocks to form the face-centered cubic crystal Ta 4 B 15 ( 3 ). The IR, Raman, and UV–vis spectra of Ta 4 B 18 ( 2 ) are theoretically simulated to facilitate its future experimental characterizations.

The extremely large magnetoresistance (XMR) effect in nonmagnetic semimetals have attracted intensive attention recently. Here we propose an XMR candidate material SrPd based on firstprinciples electronic structure calculations in combination with a semi-classical model. The calculated carrier densities in SrPd indicate that there is a good electron-hole compensation, while the calculated intrinsic carrier mobilities are as high as 10 5 cm 2 V −1 s −1 . There are only two doubly degenerate bands crossing the Fermi level for SrPd, thus a semi-classical two-band model is available for describing its transport properties. Accordingly, the magnetoresistance of SrPd under a magnetic field of 4 Tesla is predicted to reach 10 5 % at low temperature. Furthermore, the calculated topological invariant indicates that SrPd is topologically trivial. Our theoretical studies suggest that SrPd can serve as an ideal platform to examine the charge compensation mechanism of the XMR effect.