RESUMEN
The iron(III) complexes [Fe(H2O)n(OH)m]3-m (n + m = 5, 6, m ≤ 3) and corresponding proton transfer reactions are studied with total energy calculations, the nudged elastic band (NEB) method, and molecular dynamics (MD) simulations using ab initio and a modification of reactive force field potentials, the ReaxFF-AQ potentials, based on the implementation according to Böhm et al. [J. Phys. Chem. C 120, 10849-10856 (2016)]. Applying ab initio potentials, the energies for the reactions [Fe(H2O)n(OH)m]3-m + H2O â [Fe(H2O)n-1(OH)m+1]2-m + H3O+ in a gaseous environment are in good agreement with comparable theoretical results. In an aqueous (aq) or alkaline environment, with the aid of NEB computations, respective minimum energy paths with energy barriers of up to 14.6 kcal/mol and a collective transfer of protons are modeled. Within MD simulations at room temperature, a permanent transfer of protons around the iron(III) ion is observed. The information gained concerning the geometrical and energetic properties of water and the [Fe(H2O)n(OH)m]3-m complexes from the ab initio computations has been used as reference data to optimize parameters for the O-H-Fe interaction within the ReaxFF-AQ approach. For the optimized ReaxFF-AQ parameter set, the statistical properties of the basic water model, such as the radial distribution functions and the proton hopping functions, are evaluated. For the [Fe(H2O)n(OH)m]3-m complexes, it was found that while geometrical and energetic properties are in good agreement with the ab initio data for gaseous environment, the statistical properties as obtained from the MD simulations are only partly in accordance with the ab initio results for the iron(III) complexes in aqueous or alkaline environments.
RESUMEN
The interaction between oxygen vacancies and La atoms in the La doped HfO(2) dielectric were studied using first principles total energy calculations. La dopants in the vicinity of a neutral oxygen vacancy (V(O)) show lower formation energy compared to the La defects far from V(O) centres. La doping in HfO(2) leads to the shift of the defect states of oxygen vacancies towards the conduction band edge. A statistical average of this shift over several possible configurations of La atoms and V(O) shows that the incorporation of La effectively passivates the V(O) induced defect states leading to the reduction of the gate leakage current and improvement of the device reliability.
RESUMEN
In this study we investigate the silylation of OH groups with different silazanes. In particular we use density functional theory and the nudged elastic band method to study the different reaction mechanisms. For the silylation reaction of hexamethyldisilazane and trimethylaminosilane with silanol, the minimum energy paths as well as the activation and reaction energies are discussed in detail. From minimum energy reaction paths we found that all studied silazanes react exothermically. Bis(dimethylamino)dimethylsilane shows the most exothermic silylation reaction with the lowest activation energies. Therefore, it is a good candidate for the chemical repair of porous films in the semiconductor k-restoring process.