In English

Abstract

The aim of the present work is to develop a theory of high-temperature polar molecular rotors, the rotation of which is initiated by an external alternating electric field. Such rotors can be considered as Brownian motors in the sense that a unidirectional translatory motion of motor particles is similar to the unidirectional rotation of moving part of a rotor; that allows using, at calculations, the high-temperature theory of Brownian motors. The potential energy of a rotating particle, as a function of time and rotation angle, is represented in additive-multiplicative form. The approximation of the two first harmonics suffices to describe a smooth potential profile. Indeed, they are the minimum number of harmonics to simulate the asymmetry of the potential relief and to describe molecular rotors since the first harmonic is conditioned by the interaction of the rotor with the alternating field and the second one – by the potential of hindered rotation. With these conditions, the velocity of rotation of polar molecular rotors is calculated, and the analytical dependences of the velocity on the parameters of the model is analyzed for the two cases of time dependence of the applied alternating electric field, harmonic and stepped. It is shown that, at a stepped change of an alternating electric field, the values of the angular velocity are higher, for any frequency of the applied field, than those at a harmonic change, and a dichotomic mode of the electric field changing is generally more efficient one, resulting in the optimal mode of rotor operation. Moreover, there exists a qualitative difference, in the low-frequency asymptotics of the rotor velocity, between harmonic and stepwise external field: the average velocity of rotation is proportional to the square of the field modulation frequency in the former case, and it is the linear function of the frequency in the later case.