Joint Density-Functional Theory of the Electrode-Electrolyte Interface: Application to Fixed Electrode Potentials, Interfacial Capacitances, and Potentials of Zero Charge

This work explores the use of joint density-functional theory, a new form of density-functional theory for the ab initio description of electronic systems in thermodynamic equilibrium with a liquid environment, to describe electrochemical systems. After reviewing the physics of the underlying fundamental electrochemical concepts, we identify the mapping between commonly measured electrochemical observables and microscopically computable quantities within an, in principle, exact theoretical framework. We then introduce a simple, computationally efficient approximate functional which we find to be quite successful in capturing a priori basic electrochemical phenomena, including the capacitive Stern and diffusive Gouy-Chapman regions in the electrochemical double layer, quantitative values for interfacial capacitance, and electrochemical potentials of zero charge for a series of metals. We explore surface charging with applied potential and are able to place our ab initio results directly on the scale associated with the Standard Hydrogen Electrode (SHE). Finally, we provide explicit details for implementation within standard density-functional theory software packages at negligible computational cost over standard calculations carried out within vacuum environments.Comment: 18 pages, 5 figures. Initially presented at APS March Meeting 2010. Accepted for publication in Physical Review B on Jul. 27, 201

Dying with Dignity: Where is the Compassion in Compassionate Release Programs?

The prison population in the United States is on the rise. The fastest growing population in prisons are those who could be considered elderly. With the graying of our prison population comes many diseases of aging that will wreak havoc not just on the inmates, but on the costs of incarceration. Prison inmates cannot acquire their own medical care; it is the responsibility of society and hence the prison system itself. If the prisons cannot adequately care for terminally ill or elderly inmates then compassionate release should be considered. Compassionate Release Programs are designed to allow those inmates who are terminally ill or elderly to apply for early release. But it is very hard to get such petitions approved, much less understand who is truly eligible. Thus, very few inmates are being released to spend whatever time they have left with loved ones. Not only would Compassionate Release Programs save money but they would allow those inmates at the lowest risk of recidivism to die with dignity

A computationally efficacious free-energy functional for studies of inhomogeneous liquid water

We present an accurate equation of state for water based on a simple microscopic Hamiltonian, with only four parameters that are well-constrained by bulk experimental data. With one additional parameter for the range of interaction, this model yields a computationally efficient free-energy functional for inhomogeneous water which captures short-ranged correlations, cavitation energies and, with suitable long-range corrections, the non-linear dielectric response of water, making it an excellent candidate for studies of mesoscale water and for use in ab initio solvation methods.Comment: 6 pages, 5 figure

JDFTx: software for joint density-functional theory

Density-functional theory (DFT) has revolutionized computational prediction of atomic-scale properties from first principles in physics, chemistry and materials science. Continuing development of new methods is necessary for accurate predictions of new classes of materials and properties, and for connecting to nano- and mesoscale properties using coarse-grained theories. JDFTx is a fully-featured open-source electronic DFT software designed specifically to facilitate rapid development of new theories, models and algorithms. Using an algebraic formulation as an abstraction layer, compact C++11 code automatically performs well on diverse hardware including GPUs. This code hosts the development of joint density-functional theory (JDFT) that combines electronic DFT with classical DFT and continuum models of liquids for first-principles calculations of solvated and electrochemical systems. In addition, the modular nature of the code makes it easy to extend and interface with, facilitating the development of multi-scale toolkits that connect to ab initio calculations, e.g. photo-excited carrier dynamics combining electron and phonon calculations with electromagnetic simulations.Comment: 9 pages, 3 figures, 2 code listing

Secondary School English Teachers’ Perceptions of Personalized Learning

The research problem for this study was that secondary English teachers are often inconsistent in their use of personalized learning during instruction. The purpose of this basic qualitative study was to explore research questions on secondary school English teachers’ perceptions of personalized learning and challenges to its consistent use as an instructional model. The conceptual framework, self-regulated learning theory, aligns with the premise that teachers are the facilitators in a personalized learning classroom and students are engaged in self-regulating. The research questions considered the perceptions of teachers on personalized learning and the challenges they may face when implementing it with fidelity. Data collection involved semistructured interviews with nine secondary English teachers with at least 2 years of experience using one or more personalized learning models while teaching Grades 6 to 12. Transcribed data were coded and categorized to draw out themes. Three themes were used to convey the study’s findings: (a) Although teachers face some challenges, teachers believe that personalized learning models and the self-regulating strategies involved support academic achievement; (b) teachers believe that personalized learning fosters creative and collaborative opportunities for teachers; and (c) although personalized learning is perceived by teachers to support academic achievement, teachers experience technical and practical challenges that affect the implementation of personalized learning. The findings of this study contribute to positive social change because they could be used to improve instruction in the classroom, increase students’ academic achievement, inform educational leaders on how to best improve teacher performance, and provide clarity around teacher roles and responsibilities in a personalized learning environment