skip to main content

Explore Research Products in the NSF-PAR

  • NSF Public Access
  • Search Results
  • Optimizing the orbital occupation in the multiple minima problem of magnetic materials from the metaheuristic firefly algorithm
Title: Optimizing the orbital occupation in the multiple minima problem of magnetic materials from the metaheuristic firefly algorithm
We present the use and implementation of the firefly algorithm to help in scanning the multiple metastable minima of orbital occupations in density functional theory (DFT) plus Hubbard U correction and to identify the ground state occupations in strongly correlated materials. We show the application of this implementation with the Abinit code on KCoF 3 and UO 2 crystals, which are typical d and f electron systems with numerous occupation minima. We demonstrate the validity and performance of the method by comparing with previous methodologies. The method is general and can be applied to any code using constrained occupation matrices.  more » « less
Award ID(s):
1740111
NSF-PAR ID:
10185628
Author(s) / Creator(s):
; ; ; ;
Date Published:
Journal Name:
Physical Chemistry Chemical Physics
Volume:
21
Issue:
39
ISSN:
1463-9076
Page Range / eLocation ID:
21932 to 21941
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ( , International Conference on Information Systems)
    null (Ed.)
    Occupations, like many other social systems, are hierarchical. They evolve with other elements within the work ecosystem including technology and skills. This paper investigates the relationships among these elements using an approach that combines network theory and modular systems theory. A new method of using work related data to build occupation networks and theorize occupation evolution is proposed. Using this technique, structural properties of occupations are discovered by way of community detection on a knowledge network built from labor statistics, based on more than 900 occupations and 18,000 tasks. The occupation networks are compared across the work ecosystem as well as over time to understand the interdependencies between task components and the coevolution of occupation, tasks, technology, and skills. In addition, a set of conjectures are articulated based on the observations made from occupation structure comparison and change over time. 
    more » « less
  2. ; ; ; ( , The Journal of Chemical Physics)

    For an electronic system, given a mean field method and a distribution of orbital occupation numbers that are close to the natural occupations of the correlated system, we provide formal evidence and computational support to the hypothesis that the entropy (or more precisely −σS, where σ is a parameter and S is the entropy) of such a distribution is a good approximation to the correlation energy. Underpinning the formal evidence are mild assumptions: the correlation energy is strictly a functional of the occupation numbers, and the occupation numbers derive from an invertible distribution. Computational support centers around employing different mean field methods and occupation number distributions (Fermi–Dirac, Gaussian, and linear), for which our claims are verified for a series of pilot calculations involving bond breaking and chemical reactions. This work establishes a formal footing for those methods employing entropy as a measure of electronic correlation energy (e.g., i-DMFT [Wang and Baerends, Phys. Rev. Lett. 128, 013001 (2022)] and TAO-DFT [J.-D. Chai, J. Chem. Phys. 136, 154104 (2012)]) and sets the stage for the widespread use of entropy functionals for approximating the (static) electronic correlation.

     
    more » « less
  3. ; ; ; ; ( , American Behavioral Scientist)
    Automation continues to be a disruptive force in the workforce. In particular, new automated technologies are projected to replace many mid-skill jobs, potentially displacing millions of workers. Career planning agencies and other organizations can help support workers if they are able to effectively identify optimal transition occupations for displaced workers. We drew upon the 24.2 Occupational Information Network (O*NET) Database to conduct two related studies that identify alternate occupations for truck drivers, who are at risk of job loss due to the adoption of autonomous vehicles. In Study 1, we statistically compared the jobs that we identified based on different search methods using O*NET classifications based on their similarity to the knowledge, skills, values, and interests held by truck drivers. In Study 2, we conducted a survey of truck drivers to evaluate their perceptions of the occupations identified as objectively similar to their occupation. Results indicate that optimal transition occupations may be identified by searching for occupations that share skills as well as the same work activities/industry as a given occupation. These findings hold further implications for career planning organizations and policymakers to ease workforce disruption due to automation. 
    more » « less
  4. ; ( , Journal of Adolescence)
    Introduction The United States struggles with racial/ethnic disparities in STEM (science, technology, engineering, mathematics) degrees and occupations. According to situated expectancy-value theory, the experience and knowledge parents gain through STEM degrees and occupations shape the STEM support they provide and relatedly their adolescents' STEM motivational beliefs. Methods We analyzed data from the High School Longitudinal Study (N = 14,000; 50% female; Mage = 14 years old at 9th grade), which is a recent U.S. data set that surveyed a nationally representative sample of adolescents. Results and Conclusions Results showed that parent STEM support in 9th grade and adolescent STEM motivational beliefs in 11th grade were lower in families where parents did not have a STEM degree/occupation than in families where at least one parent had a STEM degree/occupation. Our within-group analyses suggested that parents' STEM support was generally positively related to adolescents' STEM motivational beliefs among families where parents did not have a STEM degree/occupation for all racial/ethnic groups except Black adolescents. However, these relations were not significant among adolescents who had a parent STEM degree/occupation. Furthermore, although Asian and White adolescents' parents were more likely to hold a STEM degree/occupation than Latina/o and Black adolescents' parents, the associations between parent STEM support and adolescents' STEM motivational beliefs emerged for Asian, Latina/o, and White adolescents. 
    more » « less
  5. ; ; ; ; ; ; ; ; ; ( , Clinical Infectious Diseases)
    Abstract Background

    More details about human movement patterns are needed to evaluate relationships between daily travel and malaria risk at finer scales. A multiagent mobility simulation model was built to simulate the movements of villagers between home and their workplaces in 2 townships in Myanmar.

     Methods

    An agent-based model (ABM) was built to simulate daily travel to and from work based on responses to a travel survey. Key elements for the ABM were land cover, travel time, travel mode, occupation, malaria prevalence, and a detailed road network. Most visited network segments for different occupations and for malaria-positive cases were extracted and compared. Data from a separate survey were used to validate the simulation.

     Results

    Mobility characteristics for different occupation groups showed that while certain patterns were shared among some groups, there were also patterns that were unique to an occupation group. Forest workers were estimated to be the most mobile occupation group, and also had the highest potential malaria exposure associated with their daily travel in Ann Township. In Singu Township, forest workers were not the most mobile group; however, they were estimated to visit regions that had higher prevalence of malaria infection over other occupation groups.

     Conclusions

    Using an ABM to simulate daily travel generated mobility patterns for different occupation groups. These spatial patterns varied by occupation. Our simulation identified occupations at a higher risk of being exposed to malaria and where these exposures were more likely to occur.

     
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email