Theoretical and experimental study of the vibrational spectra of sarkinite Mn2(AsO4)(OH) and adamite Zn2(AsO4)(OH)

- The first theoretical vibrational spectra predictions are in line with the experiment.
- Essentially, all bands in the experimental spectra are tentatively assigned.
- The number of bands in the OH-region is equal to the number of independent OH-groups.
- Employed harmonic approximation is valid particularly in the lower-frequency region.