Geometry Optimization of Crystals by the Quasi-Independent Curvilinear Coordinate Approximation

The quasi-independent curvilinear coordinate approximation (QUICCA) method [K. N\'emeth and M. Challacombe, J. Chem. Phys. {\bf 121}, 2877, (2004)] is extended to the optimization of crystal structures. We demonstrate that QUICCA is valid under periodic boundary conditions, enabling simultaneous relaxation of the lattice and atomic coordinates, as illustrated by tight optimization of polyethylene, hexagonal boron-nitride, a (10,0) carbon-nanotube, hexagonal ice, quartz and sulfur at the $\Gamma$-point RPBE/STO-3G level of theory.Comment: Submitted to Journal of Chemical Physics on 7/7/0

Linear scaling computation of the Fock matrix. IX. Parallel computation of the Coulomb matrix

We present parallelization of a quantum-chemical tree-code [J. Chem. Phys. {\bf 106}, 5526 (1997)] for linear scaling computation of the Coulomb matrix. Equal time partition [J. Chem. Phys. {\bf 118}, 9128 (2003)] is used to load balance computation of the Coulomb matrix. Equal time partition is a measurement based algorithm for domain decomposition that exploits small variation of the density between self-consistent-field cycles to achieve load balance. Efficiency of the equal time partition is illustrated by several tests involving both finite and periodic systems. It is found that equal time partition is able to deliver 91 -- 98 % efficiency with 128 processors in the most time consuming part of the Coulomb matrix calculation. The current parallel quantum chemical tree code is able to deliver 63 -- 81% overall efficiency on 128 processors with fine grained parallelism (less than two heavy atoms per processor).Comment: 7 pages, 6 figure

Violence risk assessment of Sovereign Citizens: An exploratory examination of the HCR-20 Version 3 and the TRAP-18

Sovereign Citizens comprise an understudied right-wing extremist movement in the United States who have grown in notoriety in recent years due to several high- profile instances of violence. Despite this, little empirical research has been conducted on Sovereign Citizens, including research on assessing their risk for violence. In this study, we sought to replicate and extend a prior study on Sovereign Citizen violence. Using open-source data, we added several new cases to a pre-existing dataset of violent and non-violent Sovereign Citizen incidents, yielding a total sample of 107 cases. We scored each case using the HCR-20V3 and TRAP-18 risk assessment tools. Our findings indicated that higher scores on both instruments were significantly associated with greater odds of cases being violent. We also observed that several risk factors occurred with significantly more frequency among violent cases than non-violent ones. Implications for future research and professional practice are discussed

Understanding Personality Changes in Law Enforcement Officers

Do law enforcement officers experience personality trait changes over the course of their careers? In Challacombe, Ackerman, and Stones (in press), the researchers found US-based officers had personality differences based on their lengths of service and career stress levels. The current study explores this topic by using a grounded theory approach to better understand these changes over the course of the officer’s career. We are analyzing data collected from an anonymous survey offered to sworn law enforcement officers across the United States. Initial interviewing included open ended questions that explored the participants’ experience and concerns. These individual interviews are compared and coded to identify focused categories for subsequent interviews. Theoretical sampling is being used to conduct further interviews until saturation was reached around our grounded theory categories. Officers are reporting changes in communication styles, increases in cynicism, general mistrust, and increased hypervigilance. Possible protective factors may include mastery and increased confidence as well as positive relationships within their department. The results of the study to date will be provided along with suggestions for future research

Expansion algorithm for the density matrix

A purification algorithm for expanding the single-particle density matrix in terms of the Hamiltonian operator is proposed. The scheme works with a predefined occupation and requires less than half the number of matrix-matrix multiplications compared to existing methods at low (90%) occupancy. The expansion can be used with a fixed chemical potential in which case it is an asymmetric generalization of and a substantial improvement over grand canonical McWeeny purification. It is shown that the computational complexity, measured as number of matrix multiplications, essentially is independent of system size even for metallic materials with a vanishing band gap.Comment: 5 pages, 4 figures, to appear in Phys. Rev.