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Revista mexicana de física
versión impresa ISSN 0035-001X
Rev. mex. fis. vol.50 no.4 México ago. 2004
Carta
Charged pore matrices prepared with and without template particles by computer simulations
E. Nuñeza, M. Riverab, and H. Domingueza,*
a Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, 04510 México, D.F. Tel. 52 (55) 5622 46 04, Fax. 52 (55) 56 22 46 02
b Instituto de Física, Universidad Nacional Autónoma de México, 01000 México, D.F. * E-mail: hectordc@servidor.unam.mx.
Recibido el 10 de noviembre de 2003;
Aceptado el 5 de marzo de 2004.
Abstract
Series of Molecular Dynamics simulations to study the structure of different porous matrices were investigated. Matrices were prepared by two different processes. The first method consisted of charged particles simulated at a fixed density, and after equilibration, the matrix structure was taken from the last configuration. The second method was prepared from a binary mixture of charged particles where one of the components served as the template material and the other as the matrix. The final porous matrix configuration was obtained by removing template particles from the equilibrated mixture, and therefore only the matrix particles remained in the system. The volume distribution, the cluster formation, and the porosity in the pore matrix were investigated. The present results were compared with previous results of pore matrices prepared without electrostatic interactions. Therefore, electrostatic effects were analyzed in terms of the pore matrix preparation method. As a general trend, it was observed that matrices prepared with template presented smaller voids in the structure in comparison with matrices prepared without template. It was also found that porosity was higher in matrices without template than in matrices with template. When comparisons were made between matrices with and without electrostatic interactions, the porosity was higher in matrices with charge than in matrices without charge. Finally, at low and high temperatures, the porosity values were nearly the same.
Keywords: Porous structure; porosity; charged porous matrices; computer simulation.
Resumen
Se realizaron simulaciones de Dinámica Molecular para estudiar la estructura de matrices porosas. Las matrices fueron preparadas mediante dos métodos. El primer método consistió en simular partículas cargadas a una densidad fija donde su última configuración fué la de la matriz. El segundo método utilizó una mezcla binaria de partículas cargadas donde una especie se consideró como partículas de un substrato y la otra especie como partículas de la matriz. La configuración final de la matriz se tomó después de congelar al sistema y remover las partículas del substrato. Se investigó la distribución de volúmenes, la formación de agregados y la porosidad de las matrices. Los resultados de la porosidad obtenidos se compararon con resultados anteriores para sistemas sin interacciones eléctricas. Así entonces, fue posible estudiar el efecto de la interacción electrostática en la preparación de matrices porosas. Los resultados muestran que las matrices preparadas sin partículas substrato tienen mayores cavidades que aquellas matrices preparadas con substrato. Las comparaciones entre matrices con y sin cargas muestran que la porosidad es mayor en matrices preparadas con interacciones electrostáticas. Finalmente, a altas y bajas temperaturas las porosidades fueron muy similares.
Descriptores: Estructura de poros; porosidad; matrices porosas cargadas; simulaciones por computadora.
PACS: 61.25.-f; 61.43.Bn; 61.43.Gt
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Acknowledgments
We acknowledge the support from DGAPA, UNAM through grant IN113201 and CONACyT-México through grant 37323E
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