A specific structure of doped graphene with substituted silicon impurity is introduced and ab initio density-functional approach is applied for the energy band structure calculation of the proposed structure. Using the band structure calculation for different silicon sites in the host graphene, the effect of silicon concentration and unit cell geometry on the bandgap of the proposed structure i...

The title terpene, C(30)H(46)O(3), is a 28,13β-lactone of oleanolic acid prepared with bis-muth trifluoro-methane-sulfonate (OTf), Bi(OTf)(3)·xH(2)O. All rings are trans-fused. The X-ray study shows the inversion of the orientation of 18-H in the lactonization reaction. A quantum chemical ab-initio Roothaan Hartree-Fock calculation of the equilibrium geometry of the isolated mol-ecule gives val...

With nonequilibrium Green's function approach combined with density functional theory, we perform an ab initio calculation to investigate transport properties of graphene nanoribbon (GNR) junctions self-consistently. Tight-binding approximation is applied to model the zigzag (ZGNR) electrodes, and its validity is confirmed in comparison to the GAUSSIAN03 periodic boundary condition calculation ...

We have performed an approximate ab initio calculation of vibrational properties of hydrogenated amorphous silicon (a-Si:H) using a molecular dynamics method. A 216-atom model for pure amorphous silicon (a-Si) has been employed as a starting point for our a-Si:H models with voids that were made by removing a cluster of silicon atoms out of the bulk and terminating the resulting dangling bonds w...

Nonperturbative electron-positron pair creation (the Schwinger effect) is studied based on the Dirac-Heisenberg-Wigner formalism in 1+1 dimensions. An ab initio calculation of the Schwinger effect in the presence of a simple space- and time-dependent electric field pulse is performed for the first time, allowing for the calculation of the time evolution of observable quantities such as the char...

The leading order low energy parameters like the pion decay constant or the quark condensate are well-known from “classical” low energy theorems and experiments. It is a challenge, however, to find these parameters based exclusively on an ab-initio QCD calculation. We discuss results of a quenched lattice calculation of low energy constants using the chirally improved Dirac operator. Several la...

To understand the functional mechanisms of biological macromolecular systems, investigations of both the three-dimensional geometric and electronic structures are important. Accordingly, quantum mechanical (QM) calculations are essential to obtain the properties relevant to the electronic structures of the macromolecular systems. However, because of the high computational costs, only a few hund...