<?xml version="1.0" encoding="ISO-8859-1"?><article xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<front>
<journal-meta>
<journal-id>0188-6266</journal-id>
<journal-title><![CDATA[Acta universitaria]]></journal-title>
<abbrev-journal-title><![CDATA[Acta univ]]></abbrev-journal-title>
<issn>0188-6266</issn>
<publisher>
<publisher-name><![CDATA[Universidad de Guanajuato, Dirección de Investigación y Posgrado]]></publisher-name>
</publisher>
</journal-meta>
<article-meta>
<article-id>S0188-62662021000100140</article-id>
<article-id pub-id-type="doi">10.15174/au.2021.3215</article-id>
<title-group>
<article-title xml:lang="en"><![CDATA[An estimation of the optical constants of copper based on the FEFF 9 package: an update of previous results]]></article-title>
<article-title xml:lang="es"><![CDATA[Una estimación de las constantes ópticas del cobre basada en el paquete FEFF 9: una actualización de resultados previos]]></article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Rivas Valles]]></surname>
<given-names><![CDATA[Gildardo]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
</contrib-group>
<aff id="Af1">
<institution><![CDATA[,Universidad Autónoma de Ciudad Juárez Instituto de Ingeniería y Tecnología Departamento de Física y Matemáticas]]></institution>
<addr-line><![CDATA[Juárez Chihuahua]]></addr-line>
<country>Mexico</country>
</aff>
<pub-date pub-type="pub">
<day>00</day>
<month>00</month>
<year>2021</year>
</pub-date>
<pub-date pub-type="epub">
<day>00</day>
<month>00</month>
<year>2021</year>
</pub-date>
<volume>31</volume>
<copyright-statement/>
<copyright-year/>
<self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_arttext&amp;pid=S0188-62662021000100140&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_abstract&amp;pid=S0188-62662021000100140&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_pdf&amp;pid=S0188-62662021000100140&amp;lng=en&amp;nrm=iso"></self-uri><abstract abstract-type="short" xml:lang="en"><p><![CDATA[Abstract The FEFF software package is based on a first-principles real space Green function (RSMS) scattering theory to calculate x-ray absorption fine-structure (XAFS) and forward scattering amplitudes (FSA). A procedure to obtain XAFS and FSA using FEFF version 9 is described and applied to crystalline metallic copper as an example. From this, an energy-dependent complex dielectric constant is calculated, from which other optical constants such as the complex index of refraction, absorption coefficient, reflectance, and energy-loss function are derived. The results are compared to values taken from the literature. It is found that they agree in the x-ray region; however, for photons corresponding to the ultraviolet (below 120 eV), the agreement is only qualitative.]]></p></abstract>
<abstract abstract-type="short" xml:lang="es"><p><![CDATA[Resumen El paquete de software FEFF está basado en una teoría de la dispersión basada en primeros principios de la función de Green en el espacio real (RSGF, por sus siglas en inglés) para calcular la estructura fina en la absorción de rayos X (XAFS) y la amplitud de dispersión frontal (FSA). Se describe un procedimiento para obtener XAFS y FSA utilizando FEFF versión 9, que fue aplicado al cobre cristalino metálico como ejemplo. De esto se obtiene una constante dieléctrica compleja dependiente de la energía, a partir de la cual se derivan otras constantes ópticas como el índice de refracción complejo, el coeficiente de absorción, la reflectancia y la función de pérdida de energía. Se comparan los resultados con valores tomados de la literatura. Se encuentra que estos concuerdan en la región de los rayos X; sin embargo, para fotones correspondientes al rango ultravioleta (debajo de los 120 eV), la concordancia es solo cualitativa.]]></p></abstract>
<kwd-group>
<kwd lng="en"><![CDATA[Spectroscopy]]></kwd>
<kwd lng="en"><![CDATA[optical constants]]></kwd>
<kwd lng="en"><![CDATA[first-principles calculations]]></kwd>
<kwd lng="es"><![CDATA[Espectroscopía]]></kwd>
<kwd lng="es"><![CDATA[constantes ópticas]]></kwd>
<kwd lng="es"><![CDATA[cálculo por primeros principios]]></kwd>
</kwd-group>
</article-meta>
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