The energetic characteristics of two-shell carbon nanoparticles (onions) wi
th different shapes of second shell are calculated. The barriers of relativ
e rotation of shells are found to be surprisingly small; therefore, free re
lative rotation of shells can take place at room temperature. The intershel
l orientational melting of the nanoparticle is studied by molecular dynamic
s. The parameters of the Arrhenius formula for jumprotational intershell di
ffusion are calculated. The rotation of shells can be observed beginning fr
om a temperature of 70 K. (C) 2000 Elsevier Science B.V.