Физика Низких Температур: Том 47, Выпуск 5 (Май 2021), c. 440-445 ( к оглавлению , назад )
Heavy doped organic crystals ordering
V. A. Lykah
National Technical University “Kharkiv Polytechnic Institute”, Kharkiv 61002, Ukraine
E. S. Syrkin
B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of UkraineKharkiv 61103, Ukraine
E. N. Trotskii
V. N. Karazin Kharkiv National University, Kharkiv 61022, Ukraine
Received January 14, 2021, published online March 26, 2021
The simple model that can describe structure and charge ordering in complex doped organic crystals is proposed. We consider the quasione-dimensional model of a crystal with chains (stacks) of flat BEDT-TTF molecules. In a chain of large molecules, small molecules fill every space between large molecules. The interaction between all molecules is described by the Lennard-Jones potential. It is shown that the small dopant molecules are in the double-well potential. It is shown that in case of the electrically neutral molecules at low temperatures there is a fluctuating structural ordering: the small molecules group in pairs near a large molecule, the lattice period in the fluctuation domain doubles. The structure of the boundary between the fluctuation domains is defined. In case of the charged molecules, correction to electric dipole interaction makes the system essentially three-dimensional, there is ferroelectric ordering in a chain and antiferroelectric one between the chains. Structure of the charge domains and domain boundaries are described.
Key words: molecular crystal, quasione-dimensional model, dopants, charge ordering, domain boundaries.