Professor J Halley

CSENG Physics & Astronomy
College of Science & Engineering
Twin Cities
Project Title: 
Simulations in Chemical and Condensed Matter Physics

This group studies a variety of complex many body systems providing insight at many length and time scales into the collective phenomena of interest.

  • Abstracted models of interacting polymer systems far from equilibrium. The researchers are accumulating data on the statistical distribution of chemical morphologies and dynamics. These models are intended to provide better understanding of how dynamic metastable states involving large molecules can emerge from a starting configuration of small molecules as is believed to have occurred in the origin of life. The researchers have studied a "well mixed reactor" version of such a model, an extension in which spatial heterogeneity and diffusion can occur and a model in which bond energies and energy flows are taken into account. Studies of the detailed morphological and dynamic character of the well mixed model also continue. Measures for characterizing lifelike properties of such systems have been developed and tested on real living and nonliving systems. The group found evidence that spontaneous generation of population distributions like those in living systems is most likely in quite sharply defined circumstances specified by temperature and bond energies. They are currently exploring the effects of rapid temperature quenching in such systems. They showed that data on proteomes of more than 4,000 prokaryotes may indicate that the initial proteomes of those systems formed at high temperatures  followed by such a quench around 3.5 billion years ago. Effects of activation energies of the relevant hydrolysis scission and formative ligation of peptide bonds are currently being added to the codes simulating such quenches. 
  • Quantum fluid phenomena. A current emphasis is on condensate mediated transmission using diffusion Monte Carlo methods to obtain information about excited scattering states in the strongly interacting helium four superfluid. The methods are unique and were developed by this group. Earlier published results used a guiding wave function which did not conserve particle current. The current project is to use an improved guiding wave function which removes that defect. The project is relevant to an experiment this group proposed more than a decade ago and which has been tried in various laboratories, still without a definitive result, to observe the condensate mediated transmission effect. Another quantum fluids project is the exploration of effects of disorder, and in particular of disorder induced pairing, in superconductors. The group published a description of such a model several years ago as a possible origin of high temperature superconductivity in cuprates. The general qualitative features have recently received new experimental support. A more detailed model taking explicit of both copper and oxygen in those materials has been developed and a corresponding code is operational which, among other new features, takes account of magnetic fields on the superconductivity. Recently, the group carried out first-principles DFT calculations of the electronic structure of oxygen vacancies in one of the cuprates (LSCO) in order to parametrize the tight binding model in the case that it contains significant numbers of inplane oxygen vacancies, as suggested in the earlier work. The DFT calculations support earlier suggestions concerning the electronic structure around the vacancies. Development of the disordered tight binding model is underway. 
  • Behavior of oxide water interfaces using in-house self consistent tightbinding codes. There is tremendous current interest in oxides as electrodes in a variety of technologies using aqueous electrolytes including fuel cells, batteries, and electrolyzers. Water-oxide interfaces are also a key component in corroding metal surfaces so such studies are also relevant to attempts to understand and inhibit corrosion. One current project simulates titania water interfaces with particular emphasis on new methods for calculating surface energies to understand the propensity of titania water interfaces to dissociate water.
  • Compute trajectories in the Bohm or "pilot wave" formulation of quantum mechanics. This project, which is in the exploratory stage, explores whether observable electromagnetic radiation is predicted, and, if predicted, observed, from those trajectories. The project is relevant to the ongoing discussion of the correct interpretation of quantum mechanics, which is the subject of continuing and lively debate among physicists, mathematicians, and philosophers. 

Project Investigators

Nathan Essner
Sami Farrag
Professor J Halley
Visiting Researcher Ben Frederick Intoy
Shuhui Luo
Noah Rogers
Mr. Patrick Schelling
Jacob Schulze
Qianyi Sheng
Dr. Aaron Wynveen
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