Analysis of the model-Hamiltonian

Let us now consider the adiabatic variation of the total energy, E(Qe, Qe), induced by a Eg distortion of the RhCl6 complex keeping the (3z2 — r2)0,5(x2 — y2)05 electronic configuration. In the absence of orbital degeneracy it is expected that for such a configuration E(Qe, Qe) has the form [1-3,7]  

The force constant, K, determines in the harmonic approximation by the relation 

Of course the truncated expansion in equation (1) is meaningful provided 

The first term, //reflects the linear coupling between the electronic state (displayed by lajg) and 1// )) and the E distortion mode [1-3] 

The two 2x2 matrices have zero trace following the centre of the gravity theorem [13]. The second term in equation (5), H2, corresponds to quadratic coupling and, according to symmetry requirements, depends on two independent constants, 

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