We are interested in calculating Raman spectra from DFT models for Mn-oxide minerals, such as MnO2 pyrolusite, but are not sure where to start. To the best of our knowledge, there have been very few DFT studies of materials with transition metals, that we think is probably due to modeling issues with non-spherical d-orbitals.
A 2010 paper (D.A. McKeown, M.I. Bell, and R. Caracas, “Theoretical Determination of the Raman Spectra of Single Crystal Forsterite (Mg2SiO4)”, American Mineralogist, v. 95, p. 980-986) calculated Raman spectra from a DFT model using Mg, Si, and oxygen spherical potentials for forsterite that agreed reasonably well with experimental data. Unfortunately, the sister calculation for the similar structure fayalite (Fe2SiO4) was a failure from what we presume to be incorrect modeling of Fe using spherical potentials.
There is a 2016 paper (Yu Meng, et al., “When Density Functional Approximations Meet Iron Oxides”, JCTC, v. 12. p. 5132-5144) where DFT models for 4 Fe-oxide minerals were calculated that had different degrees of agreement with experiment for some physical, magnetic, and electrical properties. Have there been any Raman calculations performed on these phases using these DFT models? If not, can Raman calculations be done on a-Fe2O3, for example, using these DFT approximations with ABINIT?
We are curious to see if these recent results for Fe-oxides can be applied to Mn-oxide phases.