Abstract
The addition of electron donors to the vacant site of defect-perovskite structure tungsten trioxide causes a series of structural and chemical phase transitions; for instance, in the well-known case of the sodium tungsten bronzes . Here we calculate the effect of the addition of electronic charge to without the complication of also including sodium ions. Our density-functional theory method enables isolation of electronic effects from the additional size, chemical, and disorder effects present in experimental samples. Our calculated low-temperature phase diagram between and moves from the initial low-temperature monoclinic phase through a second (centered) monoclinic phase, an orthorhombic phase, a tetragonal antiferroelectric, and an aristotypic cubic phase in broad agreement with the experimentally observed transformations in . Our work confirms that the observed structural transformations are driven primarily by electronic factors. We find that the dominant electronic effect is the covalent interaction between the tungsten and oxygen orbitals.
- Received 16 February 2004
DOI:https://doi.org/10.1103/PhysRevB.70.165110
©2004 American Physical Society