Brazilian Journal of Physics

p. 199-214A hybrid approach is described, which combines stochastic classical molecular dynamics and rst principles Density Functional theory to model the atomic and electronic structure of large molecular and solid-state systems. The stochastic molecular dynamics using Generalized Simulated Annealing (GSA) is based on the nonextensive statistical mechanics and thermodynamics. Examples are given of applications in linear-chain polymers, structural ceramics, impurities in metals, and pharmacological molecule-protein interactions

Physical Review D

p. 1-4Multifractal properties in the potential energy hypersurface of polypeptides and proteins are investigated. Characteristic multifractal behavior for different molecular systems is obtained from the f(α) spectra. The analysis shows that the dimension of the phase space of the problem influences the accessibility to different parts of the potential energy hypersurface. Also, we show that it is necessary to take into account the H-bond formation between amino acids in the conformational-folding search. The present findings indicate that the f(α) function describes some structural properties of a protein. The behavior of the f(α) spectra gives an alternative explanation about the Levinthal paradox. Furthermore, the anomalous temperature dependence of the Raman spin-lattice relaxation rates can be related to the perturbations in the secondary structures

EXAFS and XRD studies in synthetic Ni-Fluorohectorite

In the present work the synthetic clay mineral fluorohectorite was studied by means of an extended X-ray absorption fine structure (EXAFS) in a powder sample with the intention to observe the number of neighboring atoms to the Ni interlayer cation. In addition X-ray diffraction (XRD) was performed in order to follow the hydration states of Ni-fluorohectorite in terms of basal-spacing measurements. The sample conditions were the same for both types of experiments. The EXAFS results show that Ni2 + forms a brucite-like structure in the form of Ni(OH)2, and that this structure coexists with the clay mineral particles. This shows that the Ni atom observed by means of our EXAFS measurements is predominantly the Ni which composes the brucite-like structure and not the interlayer Ni2 + cation. In order to confirm the formation of the brucite-like structure, the EXAFS data from Ni-fluorohectorite were compared to Ni-salt water solutions at various pH