Monoclinic distortions

Bell R G, R A Jackson and C R A Catlow 1990. Computer Simulation of the Monoclinic Distortion in Silicalite. Journal of the Chemical Society Chemical Communications 10 782-783. 

The positional parameters given for GdFeOs (70) may also be applied to compounds NaMeFs and show that the Me-ions retain their special positions. They occupy the corners of a smaller, monomolecular pseudocell that is slightly monoclinicly distorted. By displacements of the fluoride ions the MeFe-octahedra are also somewhat distorted. Above all the three-dimensional linking of octahedra is not linear any more but exhibits angles of about 150° at the fluorine atoms. 

Oxides of the formula A B 03 +2 fomi a large family in which A is an alkaline earth and/or a lanthanide ion and B is titanium and/or nobium. Different members of this series are found in A2Nb207 CaTi03 (A = Ca, Sr) and Ln2Ti207 CaTi03 (Ln = La, Nd) systems. The ideal structure is orthorhombic, but monoclinic distortion often... 

Alonso, J. A., Martinez-Lope, M. J., Casais, M. T., Garcia-Munoz, J. L., and Fernandez-Diaz, M. T. (2000). Room-temperature monoclinic distortion due to charge disproportionation in 7 Ni03 perovskites with small rare-earth... 

The structure of the insulating low-temperature phase is a monoclinic distortion of the corundum structure. Structure determination (Dernier and Marezio 1970) shows that the V-V distance increases from 2.697 to 2.745 A, which across shared octahedral edges increases from 2.882 to 2.907. The average V-O distance remains constant. The material is antiferromagnetic, with a moment of 1.2/ B on... 

As shown in Table 5, the structure of Cr3S4 is built up of four anion layers. The body-centred orthorhombic unit cell (160) (a = ao, V = j/ 3 ao, c = 2 co) undergoes a slight monoclinic distortion caused by small displacements of the anions. Half the anions have five cation neighbours whereas the other half have only four. The displacements are such that each anion obtains the same charge (160). In Cr3S4 = Cr2+Cr +S4... 

Figures 8 and 9, plate 3, are lattice images of two compounds (n = 2 and n = 5 respectively) showing evidence of 180° domain walls. The c axes, normal to the dark Bi202 sheets in the plane of the image, are nearly, but not exactly, parallel in the two domains the two component c axes, C and C, are inclined at about 3°. These observations suggest that the domain walls are of 180° type and that the polar axes of both the n = 2 and n = 5 compounds deviate slightly from the Ct or c0 axes. As in Bi4Ti3012, there may be some small monoclinic distortion. Selected area diifraction patterns, nominally taken from both sides of the domain boundary, were identical, but the small size of the domain, about 50 nm across, makes the evidence from selected area diffraction inconclusive. As expected for 180° domains, the domain walls are quite thin since only a small adjustment or relaxation of the [B08] octahedra would be necessary, the structure of the wall is undoubtedly simple. As a consequence, the lines of contrast due to the A site cations are clearly visible in the neighbourhood of the wall (figure 9), with only minor distortions around the boundary (dashed line).

Fig. 8. Geometric structure of the (Oil) oriented single crystal surface of the monoclinic (distorted rutile) phase of the VO2 for a surface termination A BA. Vanadium and oxygen centers are shown as light large and dark small balls, respectively, with connecting sticks indicating nearest neighbor relations.

Arroyo y de Dompablo, M.E., and Ceder, G., Eirst-principles calculations on Li Ni02 phase stability and monoclinic distortion, J. Power Sources, 119, 654, 2003. 

Figure 11 indicates Ti + d defect states for tetragonal and monoclinic distortions of cubic rutile. The band gap of Ti02 is 3.2eV, and the C-F splitting is 2.7 eV. The solid arrows indicate transitions from the lower filled state to the two empty states for the monoclinic distortion. The experimental results presented below will be compared with the monoclinic distortion defect levels i.e., a complete removal of the two and threefold degeneracies of the Eg and T2g 3d-states, respectively. 

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