Phase transitions in the adsorbed molecular chains

• Authors: Victor Lykah , Evgen Syrkin
• Languages of publication: EN

Abstracts

EN

Rotational excitations of molecular adsorbed layers are studied theoretically. Nonlinear dynamical equations are obtained with accounting of quadrupolar interactions between molecules and freezing of translational degrees of freedom. The equilibrium positions of the molecules are found to be experimentally observed structures with alternating rotational ordering of planar rotors along the direction to the nearest neighbor (for linear or square structures) under low temperature. Dynamical analysis gives an integral of motion (energy) of the chain that in the long-wave limit leads consequently to the existence of four phases. The first one corresponds to oscillations near equilibrium ordered states. The second phase corresponds to low-energy rotational excitations along ‘valleys’ (easy directions in the effective potential) that do not destroy strong correlations between molecules while structural data can show rotational disorder (melting). The third phase corresponds to an energy that is enough to travel between ‘valleys’; only some ‘islands’ in the angle space are forbidden. Complete destruction of correlation when the energy is over the peaks of the effective potential corresponds to the fourth phase. Therefore rotational melting is a complex phenomenon that has several stages.

Keywords

EN

molecular adsorbed layer; nonlinear dynamics; rotational excitation; melting; 68.35.Rh; 79.60.Dp; 05.45.-a

• Publisher: De Gruyter Open
• Journal: Open Physics
• Year: 2005
• Volume: 3
• Issue: 1
• Pages: 61-68

Dates

published

1 - 3 - 2005

online

1 - 3 - 2005

Contributors

author

Victor Lykah

• Physics-technology dept., National Technic University “Kharkov Polytechnic Institute”, Frunze Str. 21, 61002, Kharkov, Ukraine

author

Evgen Syrkin

• Institute for Low Temperature Physics and Engineering, National Academy of Sciences of Ukraine, Lenin ave., 47, Kharkov, 61103, Ukraine

References

• [1] D. Marx, H. Wiechert: “Ordering and phase transitions in adsorbed monolayers of diatomic molecules”,Adv. Chem. Phys., Vol. XCV, (1996), pp. 213–394.
• [2] M. Born, Kun Huang:Dynamical theory of crystal lattices, Claridon Press, Oxford, 1954.
• [3] M. Toda:Teory of nonlinear lattices, Springer Series in Solid State Sciences N 20, Springer, Berlin, 1981. [Crossref]
• [4] Yu.A. Freiman, V.G. Manzhelii:Physics of Cryocrystals, Ed. A.A. Maradudin, Woodbury, NY, USA, 1996.
• [5] V.A. Lykah, E.S. Syrkin: “Rotational oscillations of molecular chain with quadrupolar interaction”,Physica status solidi (c), [to be printed].
• [6] A.J. Lichtenberg, M.A. Lieberman:Regular and stochastic motion, Springer, Berlin, Heidelberg/NY, 1983.

Identifiers

DOI

10.2478/BF02476506