ISSN 00360244, Russian Journal of Physical Chemistry A, 2010, Vol. 84, No. 12, pp. 2077–2081. © Pleiades Publishing, Ltd., 2010. Original Russian Text © D.V. Ivlev, A.A. Dyshin, M.G. Kiselev, A.M. Kolker, 2010, published in Zhurnal Fizicheskoi Khimii, 2010, Vol. 84, No. 12, pp. 2271–2275. 2077 INTRODUCTION The number of works devoted to investigating alco hols over a wide range of state parameters from vitre ous [1–3] to supercritical [4–6] has substantially increased as of late. Aliphatic alcohols are a classic example of heterofunctional molecules with a polar group on the one hand, and a hydrophobic part on the other hand. The structure and dynamic characteristics of alcohols have been studied using both experimental (Xray diffraction, NMR, IR and Raman spectros copy, neutron diffraction, dielectric relaxation) [4– 16] and computer simulation methods [10, 17–24]. In [25], the spinlattice relaxation times and chemical shifts for hydroxyl protons in methanol were measured over a wide range of state parameters. The average number of hydrogen bonds and the dependence of chemical shifts on pressure and temperature were obtained. Hoffman and Conradi [13] studied the for mation of the hydrogen bond in supercritical metha nol and ethanol. The authors of [26] used molecular dynamics (MD) to study the formation of the hydro gen bond in supercritical and liquid methanol over wide ranges of state parameters. In [24], an MD investigation of the dynamics of supercritical and liquid ethanol was presented over a wide range of temperature, from normal to 723 K, and pressures of up to 30 MPa. The authors concluded there were chain structures in the supercritical state. Similar results were obtained for supercritical tertbuthanol [14] by IR spectroscopy and MD simu lation. STRUCTURE OF MATTER AND QUANTUM CHEMISTRY Topology of HydrogenBonded Clusters in Sub and Supercritical nButhanol. Molecular Dynamics Simulation D. V. Ivlev, A. A. Dyshin, M. G. Kiselev, and A. M. Kolker Institute of Solution Chemistry, Russian Academy of Sciences, Ivanovo, 153045 Russia email: mgk@iscras.ru Received November 26, 2009 Abstract—We present the study of hydrogenbonded clusters in sub and supercritical nbuthanol by molec ular dynamics. A number of characteristics of hydrogen bonds were calculated on the basis of a geometrical criterion. It was determined that the effect of the partial reduction of the structure of condensed medium near critical point is manifested in an increase in the average number of hydrogen bonds and the first peak of the hydrogen–oxygen radial distribution function. By investigating the topology of hydrogenbonded clusters, it was shown that this reduction is determined by an increase of the fraction of molecules bound by two hydro gen bonds, and a reduction in the fraction of unbonded ones. DOI: 10.1134/S0036024410120125 Table 1. Charges on atoms of buthanol molecule Types of atoms q, e Types of atoms q, e c3 –0.0942 hc 0.0673 hc 0.0336 hc 0.0436 hc 0.0332 c3 0.1321 hc 0.0303 h1 0.0183 c3 –0.0797 h1 0.0223 hc 0.0447 oh –0.6047 hc 0.0405 ho 0.3969 c3 –0.0842 Note: hc are hydrogen atoms of the CH 3 group, c3 are carbon atoms, and oh are oxygen atoms; h1 are hydrogen atoms of the hydroxyl group. Table 2. Parameters of intermolecular interaction I II ε, kJ/mol σ, Å c3 c3 1.09 3.399670 c3 hc 0.41 3.024601 c3 h1 0.41 2.935511 c3 oh 1.52 3.233071 hc hc 0.16 2.649533 hc h1 0.16 2.560443 hc oh 0.57 2.858003 h1 h1 0.16 2.471353 h1 oh 0.57 2.768913 oh oh 2.10 3.066473 Note: I and II are the types of atoms in the first and second buthanol molecule.