The limitations of Slater's element-dependent exchange functional from analytic density functional theory

Our recent formulation of the analytic and variational Slater-Roothaan (SR) method, which uses Gaussian basis sets to variationally express the molecular orbitals, electron density and the one body effective potential of density functional theory, is reviewed. Variational fitting can be extended to the resolution of identity method,where variationality then refers to the error in each two electron integral and not to the total energy. It is proposed that the appropriate fitting functions be charge neutral and that all ab initio energies be evaluated using two-center fits of the two-electron integrals. The SR method has its root in the Slater's Xalpha method and permits an arbitrary scaling of the Slater-Gaspar-Kohn-Sham exchange-correlation potential around each atom in the system. Of several ways of choosing the scaling factors (Slater's exchange parameters), two most obvious are the Hartree-Fock (HF), alpha_HF, values and the exact atomic, alpha_EA, values. The performance of this simple analytic model with both sets for atomization energies of G2 set of 148 molecules is better than the local density approximation or the HF theory, although the errors in atomization energy are larger than the target chemical accuracy. To improve peformance for atomization energies, the SR method is reparametrized to give atomization energies of 148 molecules to be comparbale to those obtained by one of the most widely used generalized gradient approximations. The mean absolute error in ionization potentials of 49 atoms and molecules is about 0.5 eV and that in bond distances of 27 molecules is about 0.02 Angstrom. The overall good performance of the computationally efficient SR method using any reasonable set of alpha values makes it a promising method for study of large systems.Comment: 33 pages, Uses RevTex, to appear in The Journal of Chemical Physic

Bacteria of cooked meat

Citation: Dunlap, Olive B. Bacteria of cooked meat. Senior thesis, Kansas State Agricultural College, 1905.Morse Department of Special CollectionsIntroduction: It has come to be known as a universal fact that bacteria are present and can live, thrive and grow in almost any climate in which man and animals can live except in the far north. When conditions become unfavorable for their growth they form spores which resist the action of heat and cold to a far greater extent than do bacteria. Bacteria are not found in the blood of the normal healthy animal but how many of our domestic, animals are found to be perfectly sound and healthy. Out of almost every herd of cattle there will be found some animals which are diseased. I mention cattle not because they are the only animals which are subject to the infection of path - genic bacteria, for they are not, all animals are more or less subject to their action, but because cattle are such a universal source of seat for food. It is on account of the fact that people are thrown so at the mercy of ignorant and sometimes even dishonest butchers that they (the people) should be extremely careful from wham they purchase meat d also in the preparation, of the meat for the table. Most people think that by going through a process which is termed cooking bacteria will be killed. But in a majority of cases the meat is not thoroughly cooked and the organisms are not destroyed. Animals may become infected either by inhalation of contaminated air or by ingestion of any fluid or solid containing pathogenic bacteria. A great many people have the mistaken idea that anything which an animal will eat is good enough for them, and consequently all of the kitchen refuse is thrown into a common receptacle and often allowed to collect there for a day or two when it is taken and fed to the animals

Accurate molecular energies by extrapolation of atomic energies using an analytic quantum mechanical model

Using a new analytic quantum mechanical method based on Slater's Xalpha method, we show that a fairly accurate estimate of the total energy of a molecule can be obtained from the exact energies of its constituent atoms. The mean absolute error in the total energies thus determined for the G2 set of 56 molecules is about 16 kcal/mol, comparable to or better than some popular pure and hybrid density functional models.Comment: 5 pages, REVTE

An eclipsing post common-envelope system consisting of a pulsating hot subdwarf B star and a brown dwarf companion

Hot subdwarf B stars (sdBs) are evolved, core helium-burning objects located on the extreme horizontal branch. Their formation history is still puzzling as the sdB progenitors must lose nearly all of their hydrogen envelope during the red-giant phase. About half of the known sdBs are in close binaries with periods from 1.2 h to a few days, a fact that implies they experienced a common-envelope phase. Eclipsing hot subdwarf binaries (also called HW Virginis systems) are rare but important objects for determining fundamental stellar parameters. Even more significant and uncommon are those binaries containing a pulsating sdB, as the mass can be determined independently by asteroseismology. Here we present a first analysis of the eclipsing hot subdwarf binary V2008-1753. The light curve shows a total eclipse, a prominent reflection effect, and low--amplitude pulsations with periods from 150 to 180 s. An analysis of the light-- and radial velocity (RV) curves indicates a mass ratio close to $q = 0.146$, an RV semi-amplitude of $K=54.6 \,\rm kms^{-1}$, and an inclination of $i=86.8^\circ$. Combining these results with our spectroscopic determination of the surface gravity, $\log \,g = 5.83$, the best--fitting model yields an sdB mass of 0.47$M_{\rm \odot}$ and a companion mass of $69 M_{\rm Jup}$. As the latter mass is below the hydrogen-burning limit, V2008-1753 represents the first HW Vir system known consisting of a pulsating sdB and a brown dwarf companion. Consequently, it holds great potential for better constraining models of sdB binary evolution and asteroseismology.Comment: 9 pages, 8 figures, accepted for A&

Electronic and magnetic properties of some rare-earth dihydrides and dideuterides

Mössbauer spectroscopy has been used to study the electronic and magnetic properties of a number of rare-earth dihydrides and dideuterides. In stoichiometric ErH2 and DyH2, magnetic transitions and crystal field ground states have been established. In non-stoichiometric compounds DyH2+x and (Er)HoH2+x changes of the rare-earth point symmetry due to distributions in hydrogen site occupations are seen. This results in increases in the magnetic transition temperatures and distributions in the magnetic moments

Static dielectric response of icosahedral fullerenes from C60 to C2160 by an all electron density functional theory

The static dielectric response of C60, C180, C240, C540, C720, C960, C1500, and C2160 fullerenes is characterized by an all-electron density-functional method. First, the screened polarizabilities of C60, C180, C240, and C540, are determined by the finite-field method using Gaussian basis set containing 35 basis functions per atom. In the second set of calculations, the unscreened polarizabilities are calculated for fullerenes C60 through C2160 from the self-consistent Kohn-Sham orbitals and eigen-values using the sum-over-states method. The approximate screened polarizabilities, obtained by applying a correction determined within linear response theory show excellent agreement with the finite-field polarizabilities. The static dipole polarizability per atom in C2160 is (4 Angstrom^3) three times larger than that in C60 (1.344 Angstrom^3). Our results reduce the uncertainty in various theoretical models used previously to describe the dielectric response of fullerenes and show that quantum size effects in polarizability are significantly smaller than previously thought.Comment: RevTex, 3 figure

Distribution of averages in a correlated Gaussian medium as a tool for the estimation of the cluster distribution on size

Calculation of the distribution of the average value of a Gaussian random field in a finite domain is carried out for different cases. The results of the calculation demonstrate a strong dependence of the width of the distribution on the spatial correlations of the field. Comparison with the simulation results for the distribution of the size of the cluster indicates that the distribution of an average field could serve as a useful tool for the estimation of the asymptotic behavior of the distribution of the size of the clusters for "deep" clusters where value of the field on each site is much greater than the rms disorder.Comment: 15 pages, 6 figures, RevTe

High Frequency (4th order) Sequence Stratigraphy of Early Miocene Deltaic Shorelines, Offshore Texas and Louisiana

DOE-NETL Award Numbers DE-FE0026083 and DEFE0029487Bureau of Economic Geolog