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Abstract: We have studied the atomic transport coefficients namely diffusion coefficients and shear viscosities of liquid transition metals of the 3d, 4d and 5d series by applying universal scaling laws proposed by Dzugutov [Nature (London) 381, 137 (1996)] and Rosenfeld [Phys. Rev. A 15, 2545 (1977)]. The embedded atom method is used in order to describe interionic interaction in metals; and the liquid state theory is described by variational modified hypernetted chain integral equation theory. We have finally calculated excess entropy for each system, which is the main ingredient in the universal scaling law. Our results for atomic transport coefficients calculated with true excess entropy provide better agreement and also confirm the claim of Hoyt et al. [Phys. Rev. Lett 85, 594 (2000)]. [Copyright &y& Elsevier]

Abstract: An expression has been derived for radial distribution function (RDF) at contact, g(σ), for a real fluid by the use of linear isotherm regularity (LIR). This expression, which is related to intermolecular interaction, can be used to describe the temperature–density dependency of RDF at contact, g(σ,ρ,T). The expression is used for prediction of surface tension of liquid alkali metals in Evan''s expression using Lang–Kohn surface energy and in molecular dynamic results for surface tension. Application of some approximation to Evan''s expression shows that a correct selection of surface energy in the resultant expression for surface tension yields values that are in good agreement with the experiment. The surface tension of liquid alkali metals has been obtained from the molecular dynamic studies using g(σ,ρ,T) and S E/Nk B ≈ S 2/Nk B, where S 2 is related to two particle correlations. The calculated surface tension of liquid alkali metals is in good agreement with the experimental values. The calculated values of surface tension using g(σ,ρ,T) are in better agreement with the experiment than those of the hard sphere model. [Copyright &y& Elsevier]

[Display omitted] • Water molecules near the protein surface are of low density in presence of salts. • Hydrophilic residues are found to have more disruptive water structure. • Strong preferential binding affinity of Li+ with protein makes more tetrahedral water. • The entropy of the water molecules is less for Li+ near the protein surface. • Hydrogen bond life time of the water molecules decreases from interface to bulk. Water containing dissolved salts is often found to play important roles in many chemical and biological processes. They affect the stability of the amino acids and proteins by altering the liquid water structure. The formation of a mixture of non-uniform density regions in liquid water; commonly known as Low-density water and High-density water is a well-known fact experimentally; which lends uniqueness to the ubiquitous water. The behavior of these different types of water at the interface and the bulk region of the biomolecules around the hydrophobic and hydrophilic residues under the influence of different alkali metal ions, such as LiCl, NaCl, and KCl is an important unexplored question in understanding of many biomolecular processes. To address this, we carried out MD simulation of antimicrobial peptide (PDB ID: 5Z32) for two different model potentials (CHARMM-SPC/E and AMBER-TIP4P) and performed the structural analysis of water in terms of the radial distribution function, number of hydrogen bonds, orientation, tetrahedral order parameter, voids analysis to analyze the related dynamical properties like preferential binding affinity, diffusion, hydrogen bond dynamics, entropy. The water molecules around the hydrophilic environment are found to be more disruptive containing more broken hydrogen bonds in comparison to the hydrophobic environment. It is also found that the water molecules present near the protein surface are of low density and that near the bulk is of high density. This leads to the higher self-diffusion coefficient of the water molecules and less hydrogen bond lifetime at the bulk. The maximum difference is found for the solutions containing high charge density, Lithium ions. Lithium ions have a strong preferential binding affinity towards protein surface resulting in strong solvation shells containing more tetrahedral-like water structure which has low diffusion, low entropy, and higher hydrogen bond lifetime. The diffusion of the water molecules, however, increases towards the higher solvation shells. Potassium on the other hand has less preference to live on protein surfaces resulting in similar diffusion values in the bulk and interface water molecules. [ABSTRACT FROM AUTHOR]

[Display omitted] • Structure and dynamics of supercooled water were studied with two models. • Tetrahedral structure of supercooled water were examined globally and locally. • The stretched exponent of α-relaxation displays a peak in supercooled regime. • Inverse relaxation times are exponential functions of two-body excess entropy. • Water structure that causes the two-body excess entropy is illustrated. In this paper, we investigated the tetrahedral structure of supercooled water at ambient pressure and its influence on dynamic relaxation by comparing simulation results of TIP4P/2005 and SPC/E water models. The globally tetrahedral structure of supercooled water was characterized with the second-peak maximum and a deep first minimum in the radial distribution function g (r) of O-atoms and the reverse order in magnitude between the first two peaks of structure factor. The locally tetrahedral structure was specified by molecules, which and their neighbors up to the second hydration shell all have four H-bond coordinators. These molecules are referred as low-density liquid (LDL) and the others as high-density liquid (HDL). The water dynamics relaxation was studied through the self-intermediate scattering function, the non-Gaussian parameter, and the polarizability anisotropy time correlation function. Indicated by our simulations, the temperature dependence of the stretched exponent describing the α -relaxation displayed a small peak in the supercooled regime above the Widom line (WL), where LDL at the peak temperature was roughly one fourth of the total. The stretched exponent depicting the polarizability anisotropy relaxation was found to be insensitive to temperature, consistent with the experimental results. Above the WL, all relaxation times studied displayed a power-law temperature dependence with a consistent singular temperature for each model. The inverse relaxation times showed exponential functions of two-body excess entropy due to translational motions, where the entropy exhibited a logarithmic temperature behavior with a singular temperature close to that of relaxation time. This result leads to a conclusion that excess entropy is a quantity to describe dynamic relaxation of supercooled water in the thermodynamic region where the mode-coupling theory works. The water structure that causes the two-body excess entropy is illustrated and the contributions of HDL, LDL, and their mixing are also shown, where the mixing contributes significantly as near the WL. Below the WL, the formula based on the two-body excess entropy may no longer be valid. [ABSTRACT FROM AUTHOR]

The validity of Stokes−Einstein (SE) relations obtained from both slip and stick boundary conditions has been investigated for an extending temperature range approximately 250 K from the melting points of liquid Fe, Co and Ni using Dzugutov scaling scheme for transport coefficients. The basic ingredients of Dzugutov scaling scheme are the temperature dependent effective hard-sphere (HS) diameter, σ (T), and the excess entropy, S ex (T). S ex is calculated considering both two (S 2) and many body approximations (S T) of liquid atoms. For both ingredients, we have applied variational modified hypernetted chain (VMHNC) integral equation theory in conjunction with both Brettonet−Silbert (BS) pseudopotential and many body potential obtained from embedded atom method (EAM). Calculated transport coefficients using the combination of EAM and S T are in better agreement with available literature values than any other applied combinations. We observe that SE relation holds for the studied representative systems when the combination of EAM potential and S T has been considered. • VMHNC theory is successful for verification of SE relation with BS and EAM potential. • Ingredients of scaling scheme are close to experiment when EAM model has been chosen. • EAM model with many-body excess entropy provides reliable transport coefficients. • SE relation is valid when EAM model with many-body excess entropy is chosen. • For atomic diffusion the claim of Hoyt et al. has been established. [ABSTRACT FROM AUTHOR]