Pressure-Induced Metallization of a Single-Component Molecular Crystal

Abstract

The electronic structure of the single-component molecular crystal tetramethyltetratelluronapthtalene (TMTTeN) is determined at ambient and high pressure using density functional theory. The crystal is found to be a semiconductor at ambient pressure with a bandgap of 1.24 eV. The application of pressure results in a transition to a metallic state for pressures greater than 20 GPa. The onset of metallicity is the result of pressure-enhanced intermolecular interactions. Investigation of the electronic structure reveals subtle pressure-induced modifications in the nature of the HOMO and LUMO bands. Structurally, the application of pressure forms new Te-Te metallic contacts in addition to shortening the contacts present at ambient pressure. The pressure-induced increase in bandwidth may be related to the formation of these new contacts, suggesting that they are responsible for the formation of the metallic state. Our calculations indicate the molecular structure of the TMTTeN molecule is preserved; thus, the results suggest that pressure-induced metallization of single-component molecular crystals without the occurrence of molecular dissociation is possible.