Calculations of transfer integrals for tetracyanoquinodimethane salts.

Calculations of the transfer integral for the one-dimensional electron band of 7,7,8,8-tetracyanoquinodimethane (TCNQ) salts are presented. A critical discussion of the method is given, from which it follows that accurate estimates of these quantities are hard to obtain. However, relative values are expected to be more reliable. For the series of N-substituted morpholinium TCNQ salts a qualitative agreement between dc electrical conductivity and calculated transfer integral was found. For 1,2,6-trimethylpyridinium TCNQ, a counter-intuitive result is obtained, the ``crystallophic'' dimer and the ``electronic'' dimer being different.