To investigate the relationship between atomic topology, vibrational and electronic properties and superconductivity of bismuth, a 216-atom amorphous structure (a-Bi216) was computer-generated using our undermelt-quench approach. Its pair distribution function compares well with experiment. The calculated electronic and vibrational densities of states (eDOS and vDOS, respectively) show that the amorphous eDOS is about 4 times the crystalline at the Fermi energy, whereas for the vDOS the energy range of the amorphous is roughly the same as the crystalline but the shapes are quite different. A simple BCS estimate of the possible crystalline superconducting transition temperature gives an upper limit of 1.3 mK. The e-ph coupling is more preponderant in a-Bi than in crystalline bismuth (x-Bi) as indicated by the λ obtained via McMillan’s formula, λc = 0.24 and experiment λa = 2.46. Therefore with respect to x-Bi, superconductivity in a-Bi is enhanced by the higher values of λ and of eDOS at the Fermi energy.

Bismuth displays puzzling superconducting properties. In its crystalline equilibrium phase, it does not seem to superconduct at accessible low temperatures. However, in the amorphous phase it displays superconductivity at ~ 6 K. Under pressure bismuth has been found to superconduct at Tcs that go from 3.9 K to 8.5 K depending on the phase obtained. So the question is: what electronic or vibrational changes occur that explains this radical transformation in the conducting behavior of this material? In a recent publication we argue that changes in the density of electronic and vibrational states may account for the behavior observed in the amorphous phase with respect to the crystal. We have now undertaken an ab initio computational study of the effects of pressure alone maintaining the original crystalline structure and compressing our supercell computationally. From the results obtained we infer that if the crystal structure remains the same (except for the contraction), no superconductivity will appear.

Prediction of new organic photovoltaic materials in solar cells must include a precise description of charge-transfer states that are involved in electron-transfer processes such as charge separation and charge recombination which govern efficiency.

Molecular information in SMILES code was used as input in Open Babel 2.4.0 \cite{O'Boyle2011} to find the minimum energy conformer using the MMFF94 force field. The generated geometries provided the cartesian coordinates that were used to generate a Gaussian input file. In some cases, it was necessary to apply a preliminary minimization using pseudopotentials (PM7) before performing the actual DFT calculation. Molecular energies of the 156 2,2'-bipirydines were obtained using the Gaussian 16 suite at DFT, with B3LYP hybrid functional and 6-31G(d) basis. Analysis of vibrational frequencies was performed to verify the existence of an energy minimum. All geometries were optimized using both the polarizable continuum model (PCM) \cite{Miertus1981,Scalmani2010} and the solvation model based on density (SMD) \cite{Marenich2009} with water as solvent; the results presented below correspond to SMD as it is better correlated with experimental values