Crystal Structure of the Transition‐Metal Molybdates. I. Paramagnetic Alpha‐MnMoO4

Paramagnetic alpha‐MnMoO4, the stable phase at STP, is monoclinic with lattice constants a=10.469±0.005, b=9.516±0.005, c=7.143±0.005 A, and β=106°17′±6′, and space group C2/m. The crystal structure has been solved and refined by a combination of three‐dimensional Patterson and Fourier series and by the method of least squares. 1873 independent integrated intensities were measured by PEXRAD; the final agreement factor between measured and calculated structure factors is 0.0574. Two crystallographically independent Mn atoms are surrounded by highly distorted oxygen octahedra; the Mn–O distance varies between 2.091±0.006 and 2.252±0.003 A, with average length 2.164 A. Two crystallographically independent Mo atoms are surrounded by slightly distorted oxygen tetrahedra, with Mo–O distances ranging from 1.724±0.005 to 1.851±0.004 A, the average being 1.761 A. The thermal vibrations are significantly anisotropic. An analysis is given of various current methods for estimating the standard deviation in the measur...