Application of the Dimer and Tetramer Models for Interpretation of the IR Spectra of TEA(TCNQ)$\text{}_{2}$

An interpretation of the IR polarized spectra of the organic quasi-one--dimensional semiconductor triethylammonium (TCNQ)$\text{}_{2}$, between 80 and 300 K, is discussed in terms of the dimer and tetramer theories. It is concluded that the dimer model is acceptable only for describing high-T phase of TEA(TCNQ)$\text{}_{2}$. The tetramer model is more adequate for an interpretation of the IR spectra of the salt within the large temperature range. It is also shown that the phase transition influences distinctly neither vibronic (electron-molecular vibration coupled) modes nor conformity of the experimental spectra with calculated ones according to the dimer or tetramer theory.