Abstract
Monte Carlo simulation based on the Gaussian overlap model was used to study the thermodynamic properties of smectic C: C5H11O–(OH)C6H3–CH=N–C6H4–C5H11 (A), C10H21O–C6H4–CH=CH–C6H4–OC10H21 (B), ferroelectric smectic C* liquid crystals (LC): C7H15O–C6H4–C6H4–COO–CH2C*H(CH3)C2H5 (C), C8H17O–C6H4–C6H4–C2H4C*H(CH3)C2H5 (D), and an equimolar mixture of {A+C} and {A+D}. A system of N = 125 pairwise interacting ellipsoids of revolution placed in a volume V at a temperature T (that is, a system described by a canonical NVT-ensemble) is considered. These interactions were calculated using a specially devised Lennard-Jones potential, allowing for both “mild” anisotropic repulsion of particles (ellipsoids) and their dispersion attraction. Dipole–dipole interactions were also taken into account, since the molecules have highly polar groups: –O–, OH, CH=N, and COO and hence a high dipole moment (4.2-5.3 D). Calculations were carried out for a rectangular parallelepiped with periodic boundary conditions imposed on its faces. An “elementary” object of the NVT-ensemble was a two-molecule microcluster (dimer) but not a single molecule from the group under study. Smectic A ordering in the system has been unambiguously proven for different temperatures and fixed densities (0.32≤ η ≤ 0.44, where η is the close packing coefficient). The ordering is attributed to the large (transverse) dipole moment inherent in molecules {A}-{D}. Temperature dependences of free energy, configuration energy, heat capacity Cv′, and orientational order parameter were obtained. The curves agree well with the experimental data on variation of the properties of smectic LC.
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References
H. J. F. Jansen, G. Vertogen, and J. G. J. Ypma, Mol. Cryst. Liq. Cryst., 38, 445-453 (1977).
G. J. Filler, G. R. Luckhurst, and C. Zannony, J. Chem. Phys., 92, 105-115 (1985).
F. Gazi and M. Rigby, Mol. Phys., 62, No. 5, 1103-1110 (1987).
D. Frenkel, J. Phys. Chem., 92, No. 11, 3280-3284 (1988).
B. W. Van der Meer and G. Vertogen, J. Phys. Coil., 30, C3-C11 (1979).
M. A. Osipov and S. A. Pikin, Mol. Cryst. Liq. Cryst., 103, 57-68 (1983).
M. A. Osipov, Ferroelectrics, 58, 305-314 (1984).
S. Chandrasekhar, Liquid Crystals, Cambridge University Press, London (1977).
B. J. Berne and P. Pechukas, J. Chem. Phys., 56, 4213-4216 (1972).
S. M. Yailoyan, L. S. Bezhanova, and Ė. B. Abramyan, Zh. Strukt. Khim., 41, No. 4, 709-717 (2000).
A. Ts. Sarkissyan and S. M. Yailoyan, Mol. Cryst. Liq. Cryst., 241, 31-36 (1994).
H. Imura and K. Okano, J. Chem. Phys., 53, 2763-2776 (1973).
H. Marynissen, J. Thoen, and W. Van Dael, Mol. Cryst. Liq. Cryst., 97, 149-161 (1983).
I. N. Godnev, Calculation of Thermodynamic Functions from Molecular Data [in Russian], Gostekhizdat, Moscow (1956).
L. M. Sverdlov, M. A. Kovner, and E. P. Krainov, Vibrational Spectra of Polyatomic Molecules [in Russian], Nauka, Moscow (1970).
N. Kirov and P. Simova, Vibrational Spectroscopy, Sofia (1984).
W. M. Gelbart and B. Barboy, Mol. Cryst. Liq. Cryst., 33, 209-218 (1979).
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Yailoyan, S.M., Bezhanova, L.S. & Abramyan, É.B. Monte Carlo Studies of the Structural and Thermodynamic Properties of Some Smectic and Ferroelectric Liquid Crystals. Journal of Structural Chemistry 42, 181–188 (2001). https://doi.org/10.1023/A:1010438612592
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DOI: https://doi.org/10.1023/A:1010438612592