POLYMORPHIC TRANSITION IN P-DIHLORBENZOL NANOPARTICLES

Abstract. We have obtained experimentally the low frequency Raman spectra of p-dihlorbenzol nanoparticles. Nanoparticle sizes are determined with the help of electron microscope. It was found that in the lattice vibration spectra from 70 nm the summary spectrum of α-paradihlorbenzola and β-paradihlorbenzol structures appears. It agrees with both calculations of nanoparticle structure by molecular dynamics and calculations of spectra histograms of the lattice vibrations by a Dyne’s method. In the molecular crystals, the transition from massive particles to nanoparticles is accompanied by change of continuances of a lattice and orientation of molecules [1]. It can affect change of structure of a lattice and lead to phase transition. These phenomena should find reflection in change of dynamics of a lattice and accordingly in spectrums of the lattice oscillations. For studying of this question in the present operation comparison of the observational spectrums of a Raman effect of light of the lattice oscillations of nanoparticles of a p-dihlorbenzol (which has depending on temperature three updatings α, β and γ [2]) with settlement spectrums of nanoparticles has been spent at change of their size. For interpretation of a spectrum of the lattice oscillations calculations on a method the Dyne [3] are carried out. This method allows to calculate the spectrums of disorder structures and gives the chance to judge lattice parametres, dynamics of molecules and their arrangement. The nanoparticle structure was modelled by means of a method of the molecular dynamics [4]. As object of examination the organic molecular crystal of paradihlorbenzoles as it combines all necessary properties which are supposed to be explored has been chosen. Massive monocrystals of a p-dihlorbenzol are well enough studied by various methods. There is X-ray diffraction data [5] and interpretation of the lattice oscillations of this monocrystal [6]. Nanoparticles of a p-dihlorbenzol of the necessary size have been obtained. The sizes of nanoparticles were spotted on an electronic microscope. Record of spectrums of a Raman effect of light of nanoparticles was done o