Leonid Burakovsky

Melting as a dislocation-mediated phase transition

We present a theory of the melting of elements as a dislocation-mediated phase transition. We model dislocations near the melt as noninteracting closed loops on a lattice. In this framework we derive simple expressions for the melting temperature and latent heat of fusion that depend on the dislocation density at melt. We use experimental data for more than half the elements in the periodic table to determine the dislocation density from both relations. Melting temperatures yield a dislocation density of (0.61{+-}0.20)b{sup -2}, in good agreement with the density obtained from latent heats, (0.66{+-}0.11)b{sup -2}, where b is the length of the smallest perfect-dislocation Burgers vector. Melting corresponds to the situation where, on average, half of the atoms are within a dislocation core. (c) 2000 The American Physical Society.

Effective functional form of Regge trajectories

We present theoretical arguments and strong phenomenological evidence that hadronic Regge trajectories are essentially nonlinear and can be well approximated, for phenomenological purposes, by a specific square-root form. (c) 2000 The American Physical Society.

Analysis of dislocation mechanism for melting of elements: Pressure dependence

In the framework of melting as a dislocation-mediated phase transition we derive an equation for the pressure dependence of the melting temperatures of the elements valid up to pressures of order their ambient bulk moduli. Melting curves are calculated for Al, Mg, Ni, Pb, the iron group (Fe, Ru, Os), the chromium group (Cr, Mo, W), the copper group (Cu, Ag, Au), noble gases (Ne, Ar, Kr, Xe, Rn), and six actinides (Am, Cm, Np, Pa, Th, U). These calculated melting curves are in good agreement with existing data. We also discuss the apparent equivalence of our melting relation and the Lindemann criterion, and the lack of the rigorous proof of their equivalence. We show that the would-be mathematical equivalence of both formulas must manifest itself in a new relation between the Gruneisen constant, bulk and shear moduli, and the pressure derivative of the shear modulus.

An analytic model of the shear modulus at all densities and temperatures

An analytic model of the shear modulus applicable at temperatures up to melt and at all densities is presented. It is based in part on a relation between the melting temperature and the shear modulus at melt. Experimentaldata on argon are shown to agree with this relation to within 1%. The model of the shear modulus involves seven parameters, all of which can be determined from zero-pressure experimental data. We obtain the values of these parameters for 11 elemental solids. Both the experimental data on the room-temperature shear modulus of argon to compressions of ∼2.5, and theoretical calculations of the zero-temperature shear modulus of aluminum to compressions of ∼3.5 are in good agreement with the model. Electronic-structure calculations of the shear moduli of copper and gold to compressions of 2, performed by us, agree with the model to within uncertainties.

Analysis of dislocation mechanism for melting of elements

The melting of elemental solids is modeled as a dislocation-mediated transition on a lattice. Statistical mechanics of linear defects is used to obtain a new relation between melting temperature, crystal structure, atomic volume, and shear modulus that is accurate to 17% for at least half of the Periodic Table.

New relativistic high-temperature Bose-Einstein condensation.

We discuss the properties of an ideal relativistic gas of events possessing Bose-Einstein statistics. We find that the mass spectrum of such a system is bounded by

First-principles calculations on MgO: Phonon theory versus mean-field potential approach

\mu \leq m\leq 2M/\mu _K,

New quadratic baryon mass relations

where

ON THE REGGE SLOPES INTRAMULTIPLET RELATION

\mu

Towards resolution of the enigmas of P wave meson spectroscopy

is the usual chemical potential,