Since the experimental obtention of graphenen in 2004, the two dimensional crystalline systems was a study subject of strong analysis from theoretical and experimental point of view. The analytical methods goes from tight binding, Dirac equations for K and K’ points to functional density theories. The present work is an initial study of the electronic structure and the phonon frequencies spectra of 2D crystalline systems using functional density theory. We use the Exciting Fortran 90 code and GPAW Python code. The results of electronic structure for some 2D lattices are shown and also the graphene phonon frequencies spectra.

In some devices, the functionning of them is based in the interband transitions in which the electrons and holes recombine emitting photons in the visible and infrared regions. In a superlattice is formed several minibands separated by minigaps, between them may be induced intraband transitions that emitting photons in the infrarred and microwaves regions. In the present work, we develop a model that permit us calculate the probabilities per unit time of such transitions and that permit us identify the transitions used in a quantum cascade laser. We simulate two superlattice type, one with a 100 Å quantum well and the second with two dimerized quantum wells of 100 and 150 Å. In the first case, we clearly identify three cascade transitions and, in the second, we do not observe the possibility of a quantum cascade transition. But, we find a possible evidence of the competition of entangl...

The graphene, since 2004, had show some exceptional mechanical, thermal and electronic properties in se- veral configurations such as optical modulators, transistors, gas detectors, electrocromic devices, electrodes, thermal dissipaters and integrated circuits. There is an inconvenient in the atom by atom manipulation for obtain the specific properties for each function in each proposed device. We account between them, the disorder in the graphene structure and the intercalation of impurities in the hexagonal structure and the imperfections of the substrate that incorporate ripples in the graphene structure. Nevertheless, these do not modify the cones of the valence and conduction bands. The Dirac point remains. Other options has been suggested to induce a gap between the K and K′ symmetry points where lay the Dirac points in which converge the two charge carrier cones, electrons and h...