Estudio comparativo del comportamiento a alta presión de As, Sb y Bi
Ulrich Häussermann1, Karin Söderberg, Rolf Norrestam
1Department of Inorganic Chemistry, Stockholm University, S-10691 Stockholm, Sweden. ulrich@inorg.su.se
Journal of the American Chemical Society
|December 19, 2002
Resumen
La alta presión revela estructuras complejas en el arsénico, el antimonio y el bismuto. Su estabilidad surge de un equilibrio entre la energía electrostática y de banda, no de estados de valencia alterados.
Área de la Ciencia:
- Física de la materia condensada Física de la materia condensada
- Ciencia de los materiales Ciencia de los materiales.
- Química computacional es la química computacional.
Sus antecedentes:
- Los elementos del grupo 15 (As, Sb, Bi) exhiben un comportamiento estructural complejo bajo alta presión.
- La estructura Bi-III es una notable fase de alta presión caracterizada por una modulación inconmensurable.
Objetivo del estudio:
- Investigar las transiciones de fase estructural de alta presión de los elementos más pesados del grupo 15.
- Elucidar los factores electrónicos y energéticos que rigen la estabilidad de las fases de alta presión, en particular la estructura Bi-III.
Principales métodos:
- Ab initio densidad cálculos funcionales.
- Se utilizaron pseudopotenciales y un conjunto de base de onda plana para simulaciones precisas.
- Empleó aproximaciones de supercélulas para modelar la compleja estructura Bi-III.
Principales resultados:
- Reprodujo con éxito rangos de estabilidad de presión experimentales para la estructura huésped-huésped utilizando supercélulas.
- Se observó un aumento de la hibridación s-d en la estructura electrónica de As, Sb y Bi con presión, pero a un bajo nivel.
- La estabilidad de la estructura Bi-III se atribuye a un equilibrio entre las contribuciones de energía electrostática y de banda.
Conclusiones:
- Los cambios inducidos por la presión en los estados de valencia no explican la aparición de complejas estructuras de presión intermedias.
- La estabilidad de la estructura Bi-III en los elementos más pesados del grupo 15 resulta de una delicada interacción de las contribuciones de energía electrostática y de banda.
- Tanto los componentes de energía electrostática como de banda son igualmente cruciales para la estabilidad estructural en el rango de presión intermedio.
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