Resumen Una explicación de los fenómenos asociados al comportamiento de los electrones ned en una celosía periódica se propone en este documento. La dinámica de los electrones se puede determinar de manera más precisa usando la aproximación efectiva masiva. Lo haremos usando el método Hartree-Fock-Roothaan enfatizando su utilidad en sistemas típicos que requiere este modelo para estos cálculos. Una explicación y aplicación directa de este método a un problema específico de física se muestra en este documento.

Abstract One explanation of the phenomena associated to the behavior of electrons con- fned in a periodic lattice is proposed in this paper. The dynamics of the electrons can be determined more precisely using the mass efective approximation. We will carry this out using the Hartree-Fock-Roothaan method by emphasizing its usefulness in typical systems which requires this model for these calculations. An explanation and direct application of this method to a speciffic physics problem is show in this paper.

Powders Nb2 O5 were prepared by two different synthesis method, Sol-Gel and polymeric precursors (Pechini). In the Pechini method before adding the citric acid in the process, four different solutions were used to get the samples. For Sol-gel method, two different processes were also used in obtaining powders. The precursor was completely solubilized in ethanol and then hydrolyzed with ammonia and water. The calcination of the samples was between 500 and 750°C. The resulting powders were characterized by Scanning Electron Microscopy (SEM), Brunauer, Emmett and Teller (BET) surface area measurements, UV-visible and Raman spectroscopy. The formation of T−Nb2 O5 orthorhombic took place upon calcination at 7500C. Crystallite sizes were determined using the Scherrer method which resulted in an uniformed size of about 25 − 65nm. Ultraviolet-Visible diffuse reflectance spectroscopy indicated a variation in the optical band gap values (3.32-3.40 eV) in crystal growth process. The Raman vibrational modes indicate the presence of the orthorhombic phase of the material.

En este trabajo se estudia las modificaciones sufridas por el Antimoneto de Indio (InSb), crecido en la dirección [100], cuando es sometido a testes de micro-indentación mecánica, altas presiones hidrostáticas y presión por impacto. Los estudios topográficos y tomográficos de las muestras fueron hechos por medio de espectroscopia micro-Raman con diferentes longitudes de onda de la luz de excitación. El corrimiento de la posición de los fonones y el surgimiento de nuevos picos Raman permite el análisis tanto químico como estructural del sistema en estudio.

This paper studies the modifications suffered by the Indium Antimonnide (InSb), grown in the [100], when subjected to mechanical tests of micro-indentations, high hydrostatic pressure and pressure impact. Tomographic surveying and samples were made by micro-Raman spectroscopy with different wavelengths of excitation light. The shift of the position of the phonons and the emergence of new Raman peaks allow both chemical and structural analysis of the system.