E, vibration mode

It means that monoclinic structure is the result of freezing of E% vibrational mode in rhombohedral structure T point (this mode corresponds exactly to the R12 mode of ideal perovskite). 

VEs were studied. It was shown that the 22 VE trioxides COa, NOa, BOa and isovalent systems with the central atom being Si, P and Al, have minima at both Dah and Cav symmetry. The Cav minimum, at lower energy, results from vibronic coupling of the l Ai ground state with E excited states via the e vibrational mode. For GeOa, AsOa" and... 

The general principles for the construction of the vibronic Hamiltonian and the symmetry selection rules are the same as indicated above and discussed in more detail in Chapter 7. The previous distinction between trigonal and tetragonal point groups does not play a role, and the first-order coupling is always accomplished by doubly degenerate (e) vibrational modes. In an analogous notation as in Eq. (3), the Hamiltonian for the linear (E + A) (g) e pseudo-Jahn-Teller effect is found to... 

Problem 6.3 By forming the direct product x A, show that the E vibrational modes will not give a transition dipole moment in the Z-direction for the [Fe(CO)5] carbonyl stretching modes. 

The Jahn-Teller theorem predicts that distortion of TMM by an e vibrational mode should lift the D3/, degeneracy of and E. The physical reason why this is the case in TMM can easily be appreciated from Figure 12. The allyl plus p wave function for should be stabilized by an ey distortion from D h symmetry that lengthens one C-C bond and shortens the other two. The opposite phase of the same ey distortion should stabilize the ethylene plus diradical wave function for E. ... 

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