How tight is the Lieb-Oxford bound?

Density-functional theory requires ever better exchange-correlation (xc) functionals for the ever more precise description of many-body effects on electronic structure. Universal constraints on the xc energy are important ingredients in the construction of improved functionals. Here we investigate one such universal property of xc functionals: the Lieb-Oxford lower bound on the exchange-correlation energy, $E_{xc}[n] \ge -C \int d^3r n^{4/3}$, where $C\leq C_{LO}=1.68$. To this end, we perform a survey of available exact or near-exact data on xc energies of atoms, ions, molecules, solids, and some model Hamiltonians (the electron liquid, Hooke's atom and the Hubbard model). All physically realistic density distributions investigated are consistent with the tighter limit $C \leq 1$. For large classes of systems one can obtain class-specific (but not fully universal) similar bounds. The Lieb-Oxford bound with $C_{LO}=1.68$ is a key ingredient in the construction of modern xc functionals, and a substantial change in the prefactor $C$ will have consequences for the performance of these functionals.Comment: 10 pages, 3 figure

Non-empirical hyper-generalized-gradient functionals constructed from the Lieb-Oxford bound

A simple and completely general representation of the exact exchange-correlation functional of density-functional theory is derived from the universal Lieb-Oxford bound, which holds for any Coulomb-interacting system. This representation leads to an alternative point of view on popular hybrid functionals, providing a rationale for why they work and how they can be constructed. A similar representation of the exact correlation functional allows to construct fully non-empirical hyper-generalized-gradient approximations (HGGAs), radically departing from established paradigms of functional construction. Numerical tests of these HGGAs for atomic and molecular correlation energies and molecular atomization energies show that even simple HGGAs match or outperform state-of-the-art correlation functionals currently used in solid-state physics and quantum chemistry.Comment: v2: Major revison. Added information on relation to the gradient expansion and to local hybrids, improved discussion of size consistency and of performance relative to other functional

Preparation of monotectic alloys having a controlled microstructure by directional solidification under dopant-induced interface breakdown

Monotectic alloys having aligned spherical particles of rods of the minor component dispersed in a matrix of the major component are prepared by forming a melt containing predetermined amounts of the major and minor components of a chosen monotectic system, providing in the melt a dopant capable of breaking down the liquid solid interface for the chosen alloy, and directionally solidfying the melt at a selected temperature gradient and a selected rate of movement of the liquid-solid interface (growth rate). Shaping of the minor component into spheres or rods and the spacing between them are controlled by the amount of dopant and the temperature gradient and growth rate values. Specific alloy systems include Al Bi, Al Pb and Zn Bi, using a transition element such as iron

Hadron-quark mixed phase in neutron stars

Possibility of structured mixed phase at first order phase transitions is examined by taking into account of charge screening and surface effects. Hadron-quark phase transition in dense neutron star interiors is considered as a concrete example.Comment: Talk given at the 7th International Symposium on "Nuclei in the Cosmos", July 8-12,200

Work functions of self-assembled monolayers on metal surfaces

Using first-principles calculations we show that the work function of noble metals can be decreased or increased by up to 2 eV upon the adsorption of self-assembled monolayers of organic molecules. We identify the contributions to these changes for several (fluorinated) thiolate molecules adsorbed on Ag(111), Au(111) and Pt(111) surfaces. The work function of the clean metal surfaces increases in this order, but adsorption of the monolayers reverses the order completely. Bonds between the thiolate molecules and the metal surfaces generate an interface dipole, whose size is a function of the metal, but it is relatively independent of the molecules. The molecular and bond dipoles can then be added to determine the overall work function.Comment: 5 pages, 2 figure

What Is a Meretricious Relationship ?: An Analysis of Cohabitant Property Rights under \u3ci\u3eConnell v. Francisco\u3c/i\u3e

In the 1995 case Connell v. Francisco, the Supreme Court of Washington adopted an innovative and groundbreaking rule to resolve the property rights of cohabitants upon separation. After Connell, upon termination of a meretricious relationship, a trial court must perform a just and equitable distribution of the property acquired during the relationship that would have been community property had the parties been married. In adopting this rule, the supreme court sought to resolve property rights arising out of cohabitation in a predictable and equitable manner while maintaining the distinction between marriage and cohabitation. Unfortunately, the meretricious relationship fiction the court adopted as a prerequisite to ajust and equitable distribution tends to frustrate these goals. This Comment proposes that the supreme court replace the meretricious relationship fiction with a rule requiring trial courts to perform ajust and equitable distribution on the termination of any intimate cohabitation

Exact results for a charged, harmonically trapped quantum gas at arbitrary temperature and magnetic field strength

An analytical expression for the first-order density matrix of a charged, two-dimensional, harmonically confined quantum gas, in the presence of a constant magnetic field is derived. In contrast to previous results available in the literature, our expressions are exact for any temperature and magnetic field strength. We also present a novel factorization of the Bloch density matrix in the form of a simple product with a clean separation of the zero-field and field-dependent parts. This factorization provides an alternative way of analytically investigating the effects of the magnetic field on the system, and also permits the extension of our analysis to other dimensions, and/or anisotropic confinement.Comment: To appear in Phys. Rev.

The Economic Effects of New Product Beef Promotion in Guatemala

The implementation of the Central America-Dominican Republic Free Trade Agreement (CAFTA-DR) has expanded trade opportunities for U.S. agricultural producers. U.S. beef is an important product affected by the agreement, and the United States Meat Export Federation (USMEF) invested in a new product promotion program to increase exports of U.S. beef to Guatemala. Consumer responsiveness and the effectiveness of the U.S. branded beef promotion program are analyzed in this study. Demand responses to promotion activities that launched three new U.S. beef value cuts in Guatemala’s Hotel, Restaurant and Institutional (HRI) sector were estimated by applying the Parks Model of Generalized Least Squares regression to pooled, time-series and cross sectional data. Results show a negative relationship between own price and sales quantity, while the effect of advertising on quantity sold is positive. Demand for the U.S. beef value cuts increased as a result of the promotion, although the costs of the promotion program exceeded the additional revenue generated as a result of promotion activities.Livestock Production/Industries, Marketing,