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We derive a universal equation of state for compressed solids, based on thermodynamic arguments applied to virial expansions of E(p, T) and p(p, T), of the form p(v/U&)'= Ao+ A&(p/po)+ A&(p/po)T he thermal pressure is included from the beginning, and the only essential approximation is the truncation of expansions, which is justi6ed by molecular arguments. Agreement with experiment is very good for a wide range of materials, including quantum solids, noble-gas and polar-gas solids, metals, ionic compounds, and hydrocarbons. A separate assumption gives the temperature dependence of the parameters as A;( T) = A;+b; T -c; T lnT, for T )8&. The usual behavior of the Griineisen number as a function of temperature and density is accounted for in a simple way by these results.

A gradual transition from metallic to non-metallic occurs when density decreases. In the present work a thermodynamic equation of state namely the linear isotherm regularity, LIR, has been used to predict this transition. While the transition is occurring, a number of changes in the liquid structure happen and therefore a deviation from the linearity predicted by the LIR for a single-phase system is observed. The statistical mechanical theory of mixture, along with the LIR, has been used to derive an appropriate equation of state for the mixture of metal and non-metal, after the beginning of the transition. The derived equation of state is found to be (Z − 1)v 2 = a + bρ2 + cρ. In our approach only the experimental p−v−T data are required to predict such a transition for liquids Cs, Rb, Na, and Hg. The predictions are in agreement with experimental observations. It is also shown that the transition is neither first order nor second order.

A simple functional form for a general equation of state based on an effective near-neighbor pair interaction of an extended Lennard-Jones (12,6,3) type is given and tested against experimental data for a wide variety of fluids and solids. Computer simulation results for ionic liquids are used for further evaluation. For fluids, there appears to be no upper density limitation on the equation of state. The lower density limit for isotherms near the critical temperature is the critical density. The equation of state gives a good description of all types of fluids, nonpolar (including long-chain hydrocarbons), polar, hydrogen-bonded, and metallic, at temperatures ranging from the triple point to the highest temperature for which there is experimental data. For solids, the equation of state is very accurate for all types considered, including covalent, molecular, metallic, and ionic systems. The experimental pvT data available for solids does not reveal any pressure or temperature limitations. An analysis of the importance and possible underlying physical significance of the terms in the equation of state is given.

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A new linear regularity recently reported for pure dense fluids, that (Z -l)02 is linear with respect to p2, is found from experiment to be valid for mixtures as well. A simple model that mimics the regularity is used to predict the composition and temperature dependences of the two parameters of the linear isotherms. The results are used to predict the densities of some binary mixtures a t different compositions and temperatures; agreement with experiment is better than 1 %. Also, the density of a ternary system is calculated and agrees with experiment within 1.5%. The predicted composition dependences of the parameters of the linear isotherms are found to be accurate even for systems in which a stable complex forms, if the complex is considered as a separate species.

Ab initio quantum chemical calculations at the density functional theory (DFT) level were performed on eight pyridine derivative molecules as corrosion inhibitors for iron in an acidic solution. In this regard, the geometry of the molecules were optimized using the B3LYP/6-31G** method fi rst, and then interactions of these optimized structures with the iron atom were explored using the B3LYP/LANL1MB method. Two modes of adsorption were considered, i.e., planar adsorption (P) via the pyridine ring and vertical adsorption (V) through a nitrogen atom. The interaction energy was minimized through the variation of the inhibitor molecule-iron atom distance. These minimum energy values, along with the values of induced charge on the iron atom, were used to compare the inhibition power of various pairs of pyridine derivatives under consideration. Compared with the experimental data, the P orientation seems to be more satisfactory, if the minimum energy values are considered alone. However, the V orientation is in accordance with the experiment, if the induced charge on iron is considered. This is attributed to the effect of the induced charge on reducing the original surface charge of iron. It may be concluded that the P orientation is more favorable at low coverage and the V orientation at high coverage because of the excessive diminishing of the charge on the iron surface and area releasing through the P → V reorientation.