Research

In the transition region between two phases the density is an interesting function of position,   (r). This density variation is difficult to observe experimentally and hence theoretical calculations provide the most reliable characterization of interfacial regions.

Theoretical descriptions start with physical arguments about how the presence of a particle at one point in space influences the likelihood that a particle will be found at a second point. This "if I know (r) I can calculate (r)" approach leads to non-linear integral equations for  (r).

Extensive numerical work on such equations has led to the realization that they do not always possess a solution. That is, the usual engineering assumption - if an exact equation has the exact (r) as a solution, then an approximate equation will have an approximate  (r) as a solution - is incorrect for this problem. Thus the construction of an approximation requires both a reasonable estimate for multiparticle interactions and the satisfaction of an additional constraint which guarantees that the resulting integral equation actually possesses a solution. The explicit constraint has just been formulated and current work is devoted to gaining experience in applying this constraint to real problems.

Selected Publications

• "Generalization of the Stress Tensor to Nonuniform Fluids and Solids and Its Relation to Saint Venant's Strain Compatability Conditions", M. Baus and R. Lovett, Phys. Rev. Letts., 65, 1781 (1990).
• "When Does a Pair Correlation Function Fix the State of an Equilibrium System?", J. Zwicker and R. Lovett, J. Chem. Phys. 93, 6752 (1990).
• "Examples of the Construction of Integral Equations in Equilibrium Statistical Mechanics from Invariance Principles", R. Lovett and F.P. Buff, Physica A, 172, 147 (1991).
• "Do Variational Formulation for Inhomogeneous Density Functions Lead to Unique Solutions?", R. Lovett and F.H. Stillinger, J. Chem. Phys. 94, 7353 (1991).
• "Stress-strain Relations in Non-uniform Equilibrium Fluids", M. Baus and R. Lovett, Phys. Rev. A 44, 1211 (1991).
• "A Family of Equivalent Expressions for the Pressure of a Fluid Adjacent to a Wall", R. Lovett and M. Baus, J. Chem. Phys. 95, 1991 (1991).
• "Symmetry of the Pressure Tensor in a Nonuniform Fluid", M. Baus and R. Lovett, Phys. Rev. Letts. 67, 407 (1991).
• "On the Interpretation of the Radial Distribution Functions Determined from Integral Equations", L.J. Root and R. Lovett, J. Chem. Phys. 95, 8390 (1991).
• "On the Existence of Free Energy Densities in Non-uniform Fluids", R. Lovett and M. Baus, Physica A 181, 309 (1992).
• "A Direct Derivation of the Profile Equations of Buff-Lovett-Mou-Wertheim From the Born-Green-Yvon Equations for a Non-uniform Fluid", M. Baus and R. Lovett, Physica A 181, 329 (1992).
• "Two Molecular Scale Force Distributions Associated with a Planar Interface", R. Lovett and M. Baus, J. Chem. Phys. 97, 8596 (1992).
• "The Free Energy Density", R. Lovett and M. Baus, Physica A 196, 368 (1993).
• "Fluid Interfaces as Treated by Density Functional Theory", R. Lovett and M. Baus, Physica A 194, 93 (1993).
• "Thermodynamic and statistical mechanical descriptions of non-uniform fluids", R. Lovett, Physica A 213, 8 (1995).
• "Can a solid be turned into a gas without passing through a first order phase transition?", R. Lovett, in Observation, Prediction and Simulation of Phase Transtions in Complex Fluids, (edited by M. Baus, L. F. Rull and J.-P. Ryckaert (Kiuwer, Dordrecht, 1995), p. 641.
• "How a solid can be turned into a gas without passing through a first-order phase transition", S.-Y. Sheu, C.-Y. Mou and R. Lovett, Phys. Rev. E 51, 3795 (1995).
• "The magnitude and location of the surface tension of curved interfaces", M. Baus and R. Lovett, J. Chem. Phys. 103, 377 (1995).
• "A molecular theory of the Laplace relation and of the local forces in a curved interface", R. Lovett and M. Baus, J. Chem. Phys. 106(2), 635 (1997).
• "The local pressure in a cylindrical liquid-vapor interface: A simulation study", M. Mareschal, M. Baus, and R. Lovett, J. Chem. Phys. 106(2), 645 (1997).
• "The Thermodynamic Forces in an Interface", R. Lovett and M. Baus, Adv. Chem. Physics 102, 1 (1997).
• "The Solvation Free Energy of a Hard Sphere Solute in a Square Well Solvent as a Function of Solute Size", A. Ben-Naim and R. Lovett, J. Phys. Chem. B 101, 10535 (1997).
• "Van der Waals Theory for the Spatial Distribution of the Tension in an Interface. I. Density Functional Theory", J. Chem. Phys. 111, 5544 (1999).
• "Van der Waals Theory for the Spatial Distribution of the Tension in an Interface. II. Numerical Results", J. Chem. Phys. 111, 5555 (1999).
• "Simulation and the Third Law Free Energies of Face-centered-cubic and Hexagonal-close-packed Lennard-Jones Solids", S. Somasi, B. Khomami, and R. Lovett, J. Chem. Phys., 113, 4320 (2000).
• "Computer Simuation Study of the Local Pressure in Spherical Liquid-vapor Interface", H. El Bardouni, M. Mareshal, R. Lovett and M. Baus, J. Chem. Phys., 113, 9804 (2000).