Interlayer contraction inMgB2upon replacement of Mg by Al: Effect of the covalent bond energy

Abstract

The contributions of the covalent bond energies of various atom pairs to the cohesive energy of MgB2 and AlB2 are analysed with a variant of our recently developed energy-partitioning scheme for the density-functional total energy. The covalent bond energies are strongest for the intralayer B-B pairs. In contrast to the general belief, there is also a considerable covalent bonding between the layers, mediated by the metal atom. The bond energies between the various atom pairs are analysed in terms of orbital-and energy-resolved contributions. 71.15.Nc,71.20.Gj,74.25.Jb,74.72.Yg

Chelation assisted exfoliation of layered borides towards synthesizing boron based nanosheets

“…33 Another pertinent point is the nature of metal-B bond: the Al-B bond has a higher covalent bond energy (À1182 meV) when compared to the Mg-B bond (À1003 meV). 68 Thus, despite the presence of stronger metal-boron bonds in AlB 2 , the higher affinity of the EDTA molecules for the Al atoms make them much more susceptible for selective extraction from the inter gallery space by chelation. These observations suggest the opportunities available for regulating the metal:boron stoichiometries by modulating chelant-interlayer metal affinities in further studies on exfoliation of metal borides.…”

Experimental and atomistic theoretical study of degree of polarization from multilayer InAs/GaAs quantum dot stacks

“…For the stacks with three, six, and nine QD layers, the distribution of the hole wave functions is oriented along the [110] or [110] directions. This [110]/[110]symmetry is mainly due to the strain and piezoelectric potentials that lowers the overall symmetry of the QD system and favours these two directions 1,34 . To verify the impact of the strain and piezoelectricity, if we conduct a numerical experiment and switch off their contributions in the electronic structure calculations, the TE1 10 /TE 110 ratio for the L 6 system decreases from 10.92 to 0.85 and it decreases from 10.73 to 3.2 for the L 9 system.…”

A quasiclassical approach to strongly correlated quantum dots

“…We present the result as the electron-density distribution, which is an observable quantity and was recently probed in an experiment [14,15]. When the rotational symmetry is broken, the electron density directly demonstrates the formation of a Wigner crystal.…”