Inverse Dyson Equation with MP2 Self Energy

1 Methods. -3.1.1 Inverse Dyson Equation with MP2 Self Energy. - In the previous section this method was already formulated for molecules [dimers see equations (11 —(15)]. To apply it to periodic polymers one has only to substitute the level indices /, j, a, b in these equations by capital letters /, /, A, B. These capital letters stand for combined indices I = i,, J = j, ky A = a, ka and — b, . Here i etc. stands for the i-th band and k etc. for a particular quasi momentum in the band. Of course the quasi momenta have to fulfil the conservation law 

In actual calculations, especially in the case of broad bands, it can easily happen that the real part of equation (14) goes to zero. In such a case one has either to use the principal value theorem36 or can shift the denominator of (14) by a small but finite quantity.37 

Another problem is that i f one solves the non-linear system of equations (11)- 

Closing Section 3.1.1, we should like to derive the inverse Dyson equation in the diagonal approximation (equation 15), because this is not known by all chemists. One can start from the one-particle Green s matrix equation (Dyson 

Here X is the self-energy matrix, and the diagonal matrices and eHF, respectively, contain the quasi particle (correlation corrected) and the HF one- 

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Computations were performed also for the nucleotide base stacks and base pair stacks.31-34 In the case of the cytosine (C) stack we have investigated the DOS and hopping conductivity as a function of the basis set and correlation corrections (inverse Dyson equation with MP2 self energy see above). In Figure 3 we show how the DOS changes if one uses instead of an STO-3G a... 

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