This value is obviously too large. Either it is a typo, or it was calculated from the covalent or van der Waals radii of the elements.

Can you attach the paper?

Can you attach the paper?

Thanks all for your efforts. I found out that it was a typo issue because i calculated it to be 1.1980 angstroms using ionic radii in 9 fold coordination.

It is known that in crystals it is important the chemical bond, which is mainly determined by the interaction with closest neighbors. In oxide crystals (for example, with the structure of spinel, garnet, perovskite, magnetplumbite, etc.), ionic radii depend on coordination of the cations in the oxygen framework. In this case, we are dealing with the manganites, whose crystal structure contains ordered manganese ions in two oxidation states: three- and tetravalent. Mn3+ has a degenerate ground condition, might have high- and low-spin state and to be in two structurally non-equivalent positions with different orientation of the local lattice distortions. Manganese occupies the octahedral B-places with coordination number equal to 6. Calcium and lanthanum ions, even in positions with coordination number of 12, also do not have such high values of ionic radii as 1.98 A [see article by R. R. Shannon https://www.researchgate.net/publication/220037484_Revised_Effective_Ionic_Radii_and_Systematic_Study_of_Inter_Atomic_Distances_in_Halides_and_Chalcogenides]

You apparently misread the paper reported about La0.5Ca0.5MnO3. For example, I know the articles about this topic, determining the lengths of the bonds Mn–O in plane between the axial oxygen ions. [P. G. Radaelli, D. E. Cox, M. Marezio, S.-W. Cheong, Charge, orbital, and magnetic ordering in La0.5 Ca0.5 MnO3s // Physical review. B, Condensed matter 55(5) p.3015, 1997 DOI: 10.1103/PhysRevB.55.3015 https://www.researchgate.net/publication/236450954_Charge_orbital_and_magnetic_ordering_in_La05_Ca05_MnO3s;

A. Krichene, P. S. Solanki, S. Rayaprol, V. Ganesan, W. Boujelben, D. G. Kuberkar B-site of bismuth doping effect on structural, magnetic and magnetotransport properties of La0.5Ca0.5Mn1-xBixO3 // Ceramics International 41(2) p. 2637-2647, 2015 DOI: 10.1016/j.ceramint.2014.10.163 https://www.researchgate.net/publication/269106706_B-site_bismuth_doping_effect_on_structural_magnetic_and_magnetotransport_properties_of_La05Ca05Mn1-xBixO3]. And they correspond to the size you mentioned. For example, in the work by P.G. Radaelli et al. for the two nonequivalent positions, there are the following pairs of bond lengths: 2.068, 1.929 A and 2.056, 1.919 A. Average values are equal 1,9985 and 1,9875 A respectively. But they are not radii, but the distances between the centers of oxygen and manganese ions, i.e., the sum of the ionic radii of these ions.

Sincerely,

Alexander

Article Revised Effective Ionic Radii and Systematic Study of Inter ...

Article Charge, orbital, and magnetic ordering in La0.5 Ca0.5 MnO3s

Article B-site bismuth doping effect on structural, magnetic and mag...