Quasiregular impurity distribution driven by a charge-density wave

The displacive motion of impurities immersed into a one-dimensional (1D) system has been studied in detail previously as one kind of quasiregularity driven by charge-density waves (CDW’s). As a further investigation of this problem we develop here a microscopic model for a different kind of quasiregular impurity distribution driven by the CDW, consisting of a modulation in the probability of occupied sites. The dependence on impurity concentration and temperature of relevant CDW quantities is obtained. Data reported in the quasi-1D materials ${\mathrm{NbSe}}_3$ and ${\mathrm{Ta}}_2$${\mathrm{NiSe}}_7$, in particular thermal hysteresis effects at the CDW transition, are interpreted in the framework of the present model. Possible similarities to other physical systems are also suggested.