Ab initio lattice dynamics of nonconducting crystals by systematic fragmentation

A systematic method for approximating the ab initio electronic energy of crystal lattices has been improved by the incorporation of long range electrostatic and dispersion interactions. The effect of these long range interactions on the optimization of the crystal structure is reported. The harmonic lattice dynamics have been evaluated to give phonon frequencies and neutron scattering intensities. Exemplary results are reported for diamond, silicon, and α-quartz using Hartree-Fock, Möller-Plesset perturbation, and coupled-cluster levels of ab initio theory

Molecular potential energy surfaces constructed from interpolation of systematic fragment surfaces

A systematic method for approximating the ab initio electronic energy of molecules from the energies of molecular fragments has previously been presented. Here it is shown that this approach provides a feasible, systematic method for constructing a global molecular potential energy surface (PES) for reactions of a moderate-sized molecule from the corresponding surfaces for small molecular fragments. The method is demonstrated by construction of PESs for the reactions of a hydrogen atom with propane and n-pentane

Proton-transport catalysis, proton abstraction, and proton exchange in HF+HOC⁺ and H₂O+HOC⁺ and analogous deuterated reactions

Classical simulations of the reactions of HF and H₂O with HOC⁺ have been carried out on interpolatedab initiopotential energy surfaces. Rearrangement (X+HOC⁺→OCH⁺+X), abstraction (X+HOC⁺→XH⁺+OC), (X=HF or H₂O), exchange (e.g., DY+HOC⁺→HY+DOC⁺), and exchange-rearrangement (e.g., DY+HOC⁺→OCD⁺+YH) (Y=F or HO or DO) reactions are observed. However, the abstraction reaction is dominant for both the HF+HOC⁺ and H₂O+HOC⁺ systems

Ab initio energies of nonconducting crystals by systematic fragmentation

A systematic method for approximating the ab initio electronic energy of molecules from the energies of molecular fragments has been adapted to estimate the total electronic energy of crystal lattices. The fragmentation method can be employed with any ab initio electronic structure method and allows optimization of the crystal structure based on ab initio gradients. The method is demonstrated on SiO₂ polymorphs using the Hartree-Fock approximation, second order Moller-Plesset perturbation theory, and the quadratic configuration interaction method with single and double excitations and triple excitations added perturbatively

Inventory and Assessment of Cultural Resources Above the 1,551.5-Foot Contour Line, Stacy Reservoir Recreation Areas, Concho, Coleman, and Runnels Counties, Texas

In August and September 1986, personnel from Prewitt and Associates, Inc. conducted an inventory and assessment of cultural resources in five recreational area tracts above the conservation pool elevation of the proposed Stacy Reservoir in Concho, Coleman. and Runnels counties, Texas. These investigations were sponsored by the Colorado River Municipal Water District in compliance with federal requirements for a construction permit from the Corps of Engineers. Approximately 1,690 acres were surveyed. and five previously unrecorded sites were discovered and documented. Cairn feature sites 41CC213 and 41CC237 are deemed potentially significant and should be preserved or investigated to determine their significance if preservation cannot be assured. In the course of the survey. 16 previously recorded sites were encountered and. in the case of 5 of these sites. adjustments were made in their boundaries. Concurrent with the survey. 11 localities and 34 sites within the previously surveyed conservation pool area were revisited. A preliminary examination of the geologic context of these sites was conducted which resulted in recognition of important geoarcheological data potential for sites in the alluviated valleys of the project area

Molecular forces, geometries, and frequencies by systematic molecular fragmentation including embedded charges

The accuracy of energies, energy gradients, and hessians evaluated by systematic molecular fragmentation is examined for a wide range of neutral molecules, zwitterions, and ions. A protocol is established that may employ embedded charges in conjunction with fragmentation to provide accurate evaluation of minimum energy geometries and vibrational frequencies in an automated procedure

Employment Training Policies and Politics, 1980-1982 : The Transition from the Comprehensive Employment and Training Act to the Job Training Partnership Act of 1982

Dissertation (Ph.D.)--University of Kansas, American Studies, 1985

Probing the qudit depolarizing channel

For the quantum depolarizing channel with any finite dimension, we compare three schemes for channel identification: unentangled probes, probes maximally entangled with an external ancilla, and maximally entangled probe pairs. This comparison includes cases where the ancilla is itself depolarizing and where the probe is circulated back through the channel before measurement. Compared on the basis of (quantum Fisher) information gained per channel use, we find broadly that entanglement with an ancilla dominates the other two schemes, but only if entanglement is cheap relative to the cost per channel use and only if the external ancilla is well shielded from depolarization. We arrive at these results by a relatively simple analytical means. A separate, more complicated analysis for partially entangled probes shows for the qudit depolarizing channel that any amount of probe entanglement is advantageous and that the greatest advantage comes with maximal entanglement

Accuracy and efficiency of electronic energies from systematic molecular fragmentation

A systematic method for approximating the ab initio electronic energy of molecules from the energies of molecular fragments is tested on a large sample of typical organic molecular structures. The detailed methods, including some additional refinements for molecular rings and long range interactions, are described. The accuracy and computational efficiency of the systematic hierarchy of methods are reported