Hypercubane covalent crystals: Insight from density functional theory

Abstract

A series of new covalent crystals inspired by the carbon tesseract or hypercubane has been introduced using the density functional theory (DFT) calculations. Three types of possible packing of hypercubane crystals were identified: simple cubic (sc), body-centered cubic (bcc), and face-centered cubic (fcc). Based on the structure of the materials, it follows that the hypercubane crystals cannot be attributed to superdense materials, since their density is inferior to that of the diamond. An analysis of the electronic characteristics showed that crystals with sc and bcc packing belong to the class of semiconductors, whose band gaps are 2.23 and 1.46 eV, respectively, while a crystal with fcc packing possesses a metallic nature. The calculated Raman and IR spectra for semiconductor hypercubane crystals made it possible to find characteristic peaks for their identification. Thus, the characteristic IR peaks for sc hypercubane turned out to be at frequencies of 1053 and 1205 cm–1, and for the bcc hypercubane, the characteristic peak turned out to be only one at the frequency of 851 cm–1. For the Raman spectrum, the characteristic frequency values were 961 and 1300 cm−1 for sc hypercubane crystal and 1051, 1142, and 1764 cm–1 for bcc covalent hypercubane. The calculated UV–visible spectra for both the sc and bcc crystals showed an absorption maximum of ∼100 nm, which corresponds to the far UV region.