Finite size scaling as a cure for supercell approximation errors in calculations of neutral native defects in InP

The relaxed and unrelaxed formation energies of neutral antisites and interstitial defects in InP are calculated using ab initio density functional theory and simple cubic supercells of up to 512 atoms. The finite size errors in the formation energies of all the neutral defects arising from the supercell approximation are examined and corrected for using finite size scaling methods, which are shown to be a very promising approach to the problem. Elastic errors scale linearly, whilst the errors arising from charge multipole interactions between the defect and its images in the periodic boundary conditions have a linear plus a higher order term, for which a cubic provides the best fit. These latter errors are shown to be significant even for neutral defects. Instances are also presented where even the 512 atom supercell is not sufficiently converged. Instead, physically relevant results can be obtained only by finite size scaling the results of calculations in several supercells, up to and including the 512 atom cell and in extreme cases possibly even including the 1000 atom supercell.Comment: 13 pages, 11 figures. Errata in tables I and III correcte

Associations Between the School Physical Environment and Climate in Rural Schools

According to the National Center for Education Statistics (2021), more than half of all public-school districts and nearly one-third of all public-school students attend rural schools in the U.S. This study identifies characteristics of the physical environment of rural schools, considers how the physical environment of rural schools compares to urban and suburban schools, and describes the associations of a school’s physical environment with perceptions of school climate among students, staff, and parents. Using the School Assessment for Environmental Typology (SAfETy; Bradshaw et al., 2015), this study objectively assessed the physical environment of 40 rural schools in Idaho. Those characteristics were compared with data collected in prior research (Bottiani et al., 2020). This study found rural and non-rural schools, and the make-up of their physical environments, are not that different. The physical environment of rural schools had low frequencies of instances of disorder, such as trash, graffiti, drugs, paraphernalia, and evidence of building decline, such as broken windows and neglected landscaping. Rural schools also produced moderate scores related to appearance, with characteristics including illumination, visibility, and ownership. Most schools in this study were found to have interior and exterior surveillance cameras in place and employed school resource officers. Rural secondary schools in this study had a higher presence of surveillance measures than non-rural high schools, whereas non-rural high schools had higher frequencies of disorder. And, although a comparison to non-rural elementary schools is not available, the rural elementary schools score in the current study show similar physical environmental characteristics as did urban secondary schools in all three factors of the SAfETy. In addition, the current work also examined aspects of the social environment, through evaluating school climate. The Maryland Safe and Supportive (MDS3) School Climate Survey Suite was administered to students, parents, and staff in all 40 schools participating in this study. Multi-variable regression analysis was used to examine the associations between the SAfETy and school climate. Several associations were found among students, with fewer associations among staff and parents. This research study concludes that a variety of important, urgent, and malleable associations exist between a rural school’s physical environment and perceptions of school climate among students, staff, and parents. This research, and future research that builds upon this work, will assist schools as they strive to transform, strengthen, and sustain positive school environments for all stakeholders

The Destruction of the "House": Changing Social Relations in a Restructured Factory

This article explores the social changes within a dairy-products factory in Montevideo, Uruguay. Applying sociological research tools from ethnography and grounded theory, the data was collected through employment at the factory. My position as a temporary worker allowed me to interact with the many different individuals and social actors that made up the factory’s social universe. I observed major organizational shifts within the human resources department, such as the hiring of younger and more educated prospects for supervisory roles, as opposed to filling those positions with the older and more experienced workers. This shift towards “productive re-arrangement” was a consequence of the regional and commercial challenges which encouraged strategic changes to keep the company competitive. The most obvious and significant changes were found in the hiring process, when the factory began increasingly targeting temporary workers for employment. In this article, I argue that these changes were largely responsible for a new spirit and emotionality that began to emerge amongst the current working pool; one of uncertainty and mistrust. When the dairy factory altered its operating philosophy, so did its labourers. This study looks to capture the relations that developed between them

Managing the supercell approximation for charged defects in semiconductors: finite size scaling, charge correction factors, the bandgap problem and the ab initio dielectric constant

The errors arising in ab initio density functional theory studies of semiconductor point defects using the supercell approximation are analyzed. It is demonstrated that a) the leading finite size errors are inverse linear and inverse cubic in the supercell size, and b) finite size scaling over a series of supercells gives reliable isolated charged defect formation energies to around +-0.05 eV. The scaled results are used to test three correction methods. The Makov-Payne method is insufficient, but combined with the scaling parameters yields an ab initio dielectric constant of 11.6+-4.1 for InP. Gamma point corrections for defect level dispersion are completely incorrect, even for shallow levels, but re-aligning the total potential in real-space between defect and bulk cells actually corrects the electrostatic defect-defect interaction errors as well. Isolated defect energies to +-0.1 eV are then obtained using a 64 atom supercell, though this does not improve for larger cells. Finally, finite size scaling of known dopant levels shows how to treat the band gap problem: in less than about 200 atom supercells with no corrections, continuing to consider levels into the theoretical conduction band (extended gap) comes closest to experiment. However, for larger cells or when supercell approximation errors are removed, a scissors scheme stretching the theoretical band gap onto the experimental one is in fact correct.Comment: 11 pages, 3 figures (6 figure files). Accepted for Phys Rev

Mining geology in the Rosiclare fluorspar district

The Illinois-Kentucky Fluorspar district is the largest of its kind in the United States and is one of the most important in the world. It lies on either side or the Ohio River in the extreme southeastern part of Illinois and the western part of Kentucky. The mineralized area is relatively small, embracing about 1500 square miles in all. On the Illinois side, the village of Rosiclare is the center of activity. With the exception of Cave-in-Rock, practically the entire production of Illinois comes from the immediate vicinity of Rosiclare and is produced by two companies, the Rosiclare Lead and Fluorspar Mining Co. and the Hillside Fluor Spar Mines. Fluorspar is of considerable economic importance. In the steel industry and in foundry practice it is extensively used as a flux. It is of especial advantage in the basic open hearth process where it not only lessens the viscosity of the slag but materially assists in the passage or impurities into the slag. It is used in the ceramic industry in the making of certain kinds of opalescent glass. It is also the principal source for the manufacture of hydrofluoric acid and is used to some extent in the aluminum industry. From a geological standpoint the district as a whole has always attracted considerable attention. The various phases of the historical, structural, and economic geology have been abundantly discussed at different times by the most capable of authorities. In general the country is composed of nearly flat-lying sedimentaries such as limestone, shale, and sandstone, which have been extensively faulted. Some of these faults have been subsequently filled with calcite, fluorite and associated minerals to form typical fissure veins. This injection from deep-seated magmas was probably in the order as named. It is probable that mineralization and faulting were contemporaneous to some extent and that the various minerals intruded overlapped each other in the several stages of vein filling --Introduction, pages 1-2

Master of Science

thesisThe Sentinel rock avalanche in Zion National Park is one of the largest catastrophic landslide events recognized in the North American desert southwest. Originating from the western wall of Zion Canyon near its confluence with Pine Creek, the initial collapse removed a nearly 900 m high wall of predominantly Navajo sandstone. Energetic deposition is revealed by the relatively flat and hummocky topography of the debris field, which blocked flow of the Virgin River out of Zion Canyon. We combine new mapping of rock avalanche deposits with reconstruction of past topography to constrain the landslide extent, thickness, volume, and subsequent erosion. We estimate the original debris field covered an area of 3 million m2, was ~3.3 km long where it blocked the Virgin River, and had a volume of 284 million m3. The mean estimated thickness is 93 m, with a maximum deposit thickness of 200 m. Since deposition, erosion by the Virgin River has removed approximately 45%, or 131 million m3 of the Sentinel rock avalanche debris. Cosmogenic nuclide surface exposure dating of 12 boulders from across the surface of the rock avalanche deposit reveals a mean age of 4.8 ? 0.4 ka. Results further show that boulders from across the slide were deposited simultaneously, indicating a single-event, massive and catastrophic failure scenario. Numerical simulation of rock avalanche runout was performed using the 'equivalent-fluid' code DAN3D, and the results show excellent match to our mapped deposit extents and estimated thickness. The simulated rock avalanche crossed Zion Canyon in only ~20 s, with maximum velocities exceeding 90 m/s, ran up the opposing wall, and spread laterally up and down canyon. The Virgin River was dammed by landslide debris, which formed the extensive Sentinel Lake, eventually trapping a vast quantity of lacustrine and alluvial sediment. The cumulative effects reveal the long-lasting and diverse impacts of large rock avalanches in desert canyons of the Colorado Plateau: in addition to representing an extreme magnitude hazard, large landslides events also have wide-ranging ecological and geomorphic effects, here helping create the flat valley floor of Zion Canyon

Marital Outcomes and Attachment in Children of Divorce Versus Children of Intact Families

Previous studies have investigated many aspects of the lives of children of divorce, including delinquency, emotional aspects, and attachment; however, they have not investigated the patterns of marital partnership formation and persistence among children of divorce who were raised in long-term blended families versus children of other types of families. Based on attachment theory, this study compared adult children from 4 family types: children of divorce raised in (a) long-term blended families, (b) single parent families postdivorce, (c) serial matrimony families postdivorce, and (d) children raised in intact families. A quantitative, causal-comparative, ex post facto survey design was employed with a convenience sample of 674 adults 18 to 99 years of age. The family types were compared on attachment patterns using the Experiences in Close Relationships-Relationship Structures scale and on marital outcomes obtained using a demographic questionnaire. Results indicated that children of divorce raised in both serial matrimony and blended families are significantly more likely to be insecurely attached to their parents. Children of these 2 family types are also significantly more likely to divorce. The implications of these research findings may help educate parents and mental health practitioners regarding the different experiences that children of divorce experience in terms of attachment that can mitigate the effects of divorce and other difficulties that children of divorce may have in their later relationships

Correlations between magnetic properties and bond formation in Rh–MgO(001)

We present the results of first principles calculations for the magnetism of Rh adlayers on MgO (001), at three different adsorption sites and three different coverages, corresponding to 1, 1/2 and 1/8 monolayers. Finite magnetization is found in all cases except that of 1 Rh monolayer above the oxygen site, which is also the most stable. We examine how the magnetization changes as a function of the Rh-surface distance and relate this to changes in the real space charge density and in the density of states (DOS) as the Rh adlayer interacts with the surface. We find that increasing either the Rh-Rh interaction strength or the R h-surface interaction strength leads to reduced magnetization, while increasing the former drives a crossover from localized (atomic) to itinerant magnetism. Neither the magnetic transition itself, nor the localized-to-itinerant magnetism crossover, is found to be directly related to the formation of Rh- surface bonds. From a practical point of view, we predict that magnetism in the Rh-MgO(001) system is most likely to be found experimentally at reduced coverages and at low temperatures