Prediction of many-electron wavefunctions using atomic potentials: refinements and extensions to transition metals and large systems

For a given many-electron molecule, it is possible to define a corresponding one-electron Schr\"odinger equation, using potentials derived from simple atomic densities, whose solution predicts fairly accurate molecular orbitals for single- and multi-determinant wavefunctions for the molecule. The energy is not predicted and must be evaluated by calculating Coulomb and exchange interactions over the predicted orbitals. Transferable potentials for first-row atoms and transition metal oxides that can be used without modification in different molecules are reported. For improved accuracy, molecular wavefunctions can be refined by slightly scaling nuclear charges and by introducing potentials optimized for functional groups. For a test set of 20 molecules representing different bonding environments, the transferable potentials with scaling give wavefunctions with energies that deviate from exact self-consistent field or configuration interaction energies by less than 0.05 eV and 0.02 eV per bond or valence electron pair, respectively. Applications to the ground and excited states of a Ti18O36 nanoparticle and chlorophyll-s are reported.Comment: 20 pages. arXiv admin note: text overlap with arXiv:1702.0685

Prediction of many-electron wavefunctions using atomic potentials: extended basis sets and molecular dissociation

A one-electron Schroedinger equation based on special one-electron potentials for atoms is shown to exist that produces orbitals for an arbitrary molecule that are sufficiently accurate to be used without modification to construct single- and multi-determinant wavefunctions. The exact Hamiltonian is used to calculate the energy variationally and to generate configuration interaction expansions. Earlier work on equilibrium geometries is extended to larger basis sets and molecular dissociation. For a test set of molecules representing different bonding environments, a single set of invariant atomic potentials gives wavefunctions with energies that deviate from configuration interaction energies based on SCF orbitals by less than 0.04 eV per bond or valence electron pair. On a single diagonalization of the Fock matrix, the corresponding errors are reduced 0.01 eV. Atomization energies are also in good agreement with CI values based on canonical SCF orbitals. Configuration interaction applications to single bond dissociations of water and glycine, and multiple bond dissociations of ethylene and oxygen produce dissociation energy curves in close agreement with CI calculations based on canonical SCF orbitals for the entire range of internuclear distances

Roman roads in the Upper Galilee and Lower Golan regions: Relationships to natural migratory routes

The geoarchaeological problem herein was to identify the Roman roads in the Upper Galilee and Lower Golan regions of Israel. The primary objective was to identify an anthropogenic relationship of land use as a function of the physical geography of the region. The secondary objective was to identify the most favorable routes of passage to the ancient city of Bethsaida. This thesis pursued a multi-disciplinary approach to meeting the objectives. Field investigation was conducted to acquire data on the elevation, slope, aspect, lithology, and hydrology of the terrain regarding cost factor values of travel by foot. An archaeological investigation was conducted in conjunction with the field investigation to acquire data regarding the spatial distribution of Roman road remnants and artifacts on the landscape. Finally, a Geographic Information Systems (GIS) investigation was conducted to implement spatial analysis by devising a Site Suitability Analysis Process which ranked and weighted the physical geography data layers of slope, aspect, hydrology, lithology, and probable estuarine coastline. The process included generating a map of Surface Friction from the ranked and weighted values, and generating a model of Areas of Favorable Passage. This analysis facilitated identification of areas favorable for passage over varied terrain by taking into consideration the cost factor values of travel over a friction surface

Estimates of electron correlation based on density expansions

Methods for estimating the correlation energy of molecules and other electronic systems are discussed based on the assumption that the correlation energy can be partitioned between atomic regions. In one method, the electron density is expanded in terms of atomic contributions using rigorous electron repulsion bounds, and, in a second method, correlation contributions are associated with basis function pairs. The methods do not consider the detailed nature of localized excitations, but instead define a correlation energy per electron factor that that is unique to a specific atom. The correlation factors are basis function dependent and are determined by from configuration interaction calculations on diatomic and hydride molecules. The correlation energy estimates are compared with the results of high-level configuration interaction calculations for a test set of twenty-seven molecules representing a wide range of bonding environments (average error of 2.6%). An extension based on truncated CI calculations in which d- and hydrogen p-type functions are eliminated from the virtual space combined with estimates of dynamical correlation contributions using atomic correlation factors is discussed and applied to the dissociation of several molecules.Comment: 22 pages, 4 figure

An assessment of the effect of supersonic aircraft operations on the stratospheric ozone content

An assessment of the potential effect on stratospheric ozone of an advanced supersonic transport operations is presented. This assessment, which was undertaken because of NASA's desire for an up-to-date evaluation to guide programs for the development of supersonic technology and improved aircraft engine designs, uses the most recent chemical reaction rate data. From the results of the present assessment it would appear that realistic fleet sizes should not cause concern with regard to the depletion of the total ozone overburden. For example, the NOx emission of one type designed to cruise at 20 km altitude will cause the ozone overburden to increase by 0.03% to 0.12%, depending upon which vertical transport is used. These ozone changes can be compared with the predictions of a 1.74% ozone decrease (for 100 Large SST's flying at 20 km) made in 1974 by the FAA's Climatic Impact Assessment Program

When the Fourth Estate Becomes a Fifth Column: The Effect of Media Freedom and Social Intolerance on Civil Conflict

Media freedom is typically viewed as crucial to democracy and development. The idea is that independent news media will facilitate free and fair elections and shine a spotlight on corruption—thereby serving as a fourth estate. Yet political leaders often justify restricting media freedom on the grounds that irresponsible news coverage will incite political violence—potentially undermining government and in effect acting as a fifth column. So is media freedom a force for democracy or a source of civil conflict? We hypothesize that the effect of media freedom on civil conflict is conditioned by a country’s level of intolerance. Specifically, we predict when social intolerance is low, media freedom will discourage domestic conflict because the tone of the news coverage will reflect the level of tolerance and ameliorate any inflammatory coverage. In contrast, we predict that high levels of social intolerance will fuel and be fueled by inflammatory news coverage if the media are free, thereby promoting civil conflict. We test our hypotheses across countries and over time drawing from World Values and European Values Surveys and the Global Media Freedom Dataset and find that the combination of media freedom and high social intolerance is associated with increased civil conflict