title: Frequency dependence of the quasi-soft Raman-active modes in rotationally distorted R(3+)B(3+)O3 perovskites (R(3+)-rare earth, B(3+)=Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Ga).
abstract: The structural data and Raman spectra of distorted R(3+)B(3+)O(3) perovskites (R(3+)-rare earth, B(3+)=Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Ga) with BO(6) octahedral tilts were critically reviewed in order to obtain the frequency (ω) versus BO(6) tilt angle (α) dependence of the quasi-soft vibrational modes. It was found that the relation ω = ϰα is satisfied in a good approximation for each RBO(3) family with fixed B atom, despite the different spatial tilt orientations for compounds of the same series with either orthorhombic Pnma or rhombohedral R ̅3c structure. The dependence of the proportionality coefficient ϰ on the averaged <B-O> octahedral distance can be described using different functions (power, linear and exponential ones). The established dependences can be used for analysis of Raman data and heuristic prediction of structural second-order transitions.
authors.affiliation: Faculty of Physics, University of Sofia, BG-1164 Sofia, Bulgaria. neno@phys.uni-sofia.bg
authors.forename: N D
authors.initials: ND
authors.lastname: Todorov
authors.forename: M V
authors.initials: MV
authors.lastname: Abrashev
authors.forename: V G
authors.initials: VG
authors.lastname: Ivanov
mesh_terms: D001895:Boron / Q000737:chemistry; D017610:Calcium Compounds / Q000737:chemistry*; D056831:Coordination Complexes / Q000737:chemistry*; D018360:Crystallography, X-Ray; D007501:Iron / Q000737:chemistry*; D008674:Metals, Rare Earth / Q000737:chemistry*; D008958:Models, Molecular; D015233:Models, Statistical; D008968:Molecular Conformation; D010087:Oxides / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry; D015203:Reproducibility of Results; D013059:Spectrum Analysis, Raman / Q000379:methods*; D013696:Temperature; D014025:Titanium / Q000737:chemistry*; D014732:Vibration
chemical_list: D017610:Calcium Compounds; D056831:Coordination Complexes; D008674:Metals, Rare Earth; D010087:Oxides; C059910:perovskite; D014025:Titanium; D007501:Iron; D001895:Boron; D010100:Oxygen