  We measured low-frequency Raman spectra of paradibromobenzene nanoparticles.
With the reduction of the nanoparticles size frequencies of lines become
smaller and the doubling of the most intensive lines takes place. Additional
lines with increasing intensity appear in the spectrum. We did structure
calculations for nanoparticles by the method of molecular dynamics and obtained
histograms of lattice vibrations spectra by the Dyne's method. Calculations
have shown that doubling of lines is due to the appearance of nanoparticles
vibrations from borders of the Brillouin zone in the spectrum. Additional lines
are caused by vibrations with $K \neq 0$. They have mixed
orientation-translational character (that is evident from the eigenvectors of
vibrations) that affects intensity of these lines. Upon reduction of the
particles sizes change of vibration eigenvectors of molecules occurs $K \neq
0$. The greatest changes observed for a 20 cm$^{-1}$ paradibromobenzene line.
