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La autorregulación de carga al cambiar el estado de oxidación de los metales de transición en los aislantes
Hannes Raebiger1, Stephan Lany, Alex Zunger
1National Renewable Energy Laboratory, Golden, Colorado 80401, USA. hannes_raebiger@nrel.gov
Nature
|June 6, 2008
Resumen
Los átomos de metales de transición mantienen una carga local constante debido a un mecanismo de retroalimentación negativa, no a una transferencia literal de carga. Esto explica las firmas del estado de oxidación observadas en la ciencia de los materiales.
Área de la Ciencia:
- Física del estado sólido Física del estado sólido
- Ciencia de los materiales Ciencia de los materiales.
- Química cuántica es la química cuántica.
Sus antecedentes:
- Los átomos de metales de transición en los cristales exhiben diferentes estados de oxidación y radios iónicos.
- Estas variaciones se explican tradicionalmente por modelos de transferencia de carga, lo que implica el movimiento literal de electrones.
- Los cálculos de los primeros principios revelan cambios mínimos de carga local con alteración del estado de oxidación.
Objetivo del estudio:
- Para explicar las firmas del estado de oxidación observadas en los metales de transición.
- Desafiar el paradigma convencional de transferencia de carga en la física de la materia condensada.
- Para aclarar el mecanismo subyacente de la regulación de la carga en los compuestos de metales de transición.
Principales métodos:
- Primeros principios de los cálculos de la mecánica cuántica.
- Análisis de los desplazamientos a nivel del núcleo de la espectroscopia de fotoemisión de rayos X (XPS).
- Investigación de las variaciones de los radios iónicos.
- Examen de los cambios de magnetización local.
Principales resultados:
- Los átomos de metales de transición exhiben un mecanismo de retroalimentación negativa similar a la homeostasis.
- Esta retroalimentación mantiene una carga local casi constante a pesar de las perturbaciones externas.
- Las firmas observadas como los desplazamientos XPS y los cambios en los radios iónicos son consecuencias de esta regulación de la carga, no de la transferencia literal de carga.
- Los fenómenos de multivalencia se explican por esta regulación de la carga inherente.
Conclusiones:
- El paradigma de transferencia de carga para los estados de oxidación de metales de transición es reevaluado.
- Un nuevo mecanismo de regulación de la carga de retroalimentación negativa gobierna el comportamiento de los metales de transición en los cristales.
- Este hallazgo tiene un impacto en la comprensión de las propiedades de los materiales y el diseño de nuevos materiales.
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