We report the static (ε0) and high frequency (ε∞) dielectric constants of haematite (α -Fe 2O3) as calculated using density functional perturbation theory. The values for bulk iron oxide are ε011 = 26.41; ε033 = 17.84; ε∞ 11 = 7.87 and ε∞33 = 7.57. The effective static dielectric screening of porous thin-films is predicted in aqueous solutions, using effective medium theory, to range between 33 and 44 depending on the crystal packing density. The large spread in literature values (12-120) can only be explained through surface and micro-structuring effects. These results will be important for interpreting and modelling the materials behaviour, particularly in electrochemical and photoelectrochemical cells.
Bibliographical noteFunding Information:
We acknowledge L.M. Peter for suggesting the problem, useful discussions with F. Marken and K.T. Butler. R.L. was funded by a Royal Society Summer Studentship, while A.J.J. is funded by EPSRC (Grant No. EP/G03768X/1 ). Access to the HECToR supercomputer was facilitated through membership of the HPC Materials Chemistry Consortium, which is funded by EPSRC (Grant No. EP/F067496 ).
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry