Flexible 2D Crystals of Polycyclic Aromatics Stabilized by Static Distortion Waves.

The epitaxy of many organic films on inorganic substrates can be classified within the framework of rigid lattices which helps to understand the origin of energy gain driving the epitaxy of the films. Yet, there are adsorbate-substrate combinations with distinct mutual orientations for which this classification fails and epitaxy cannot be explained within a rigid lattice concept. It has been proposed that tiny shifts in atomic positions away from ideal lattice points, so-called static distortion waves (SDWs), are responsible for the observed orientational epitaxy in such cases.

Optical absorption and emission of α-Sn nanocrystals from first principles.

We investigate the optical properties of hydrogenated α-Sn nanocrystals up to diameters of 3.6 nm in the framework of an ab initio pseudopotential method including spin-orbit interaction (SOI) and the repeated supercell approximation. The fundamental absorption and emission edges are determined including quasiparticle effects and electron-hole interaction.

Massive Dirac quasiparticles in the optical absorbance of graphene, silicene, germanene, and tinene.

We present first-principles studies of the optical absorbance of the group IV honeycomb crystals graphene, silicene, germanene, and tinene. We account for many-body effects on the optical properties by using the non-local hybrid functional HSE06. The optical absorption peaks are blueshifted due to quasiparticle corrections, while the influence on the low-frequency absorbance remains unchanged and reduces to a universal value related to the Sommerfeld fine structure constant.