# Don Nicholson, Ph.D.

**Research Professor of Physics**

## Contact Information

- dnichol1@unca.edu

Don Nicholson came to our department after retiring from Oak Ridge National Laboratory (ORNL) in 2014 where was a computational materials scientist. While at ORNL he developed methods that describe from first principles the properties of metals. His approach uses the most powerful computers in the world to solve the quantum mechanical equations that determine how electrons bond metals together and how electrons flow through metals. For this work he received three Gordon Bell Prizes, a Department of Energy Outstanding Research Award, and was named a Smithsonian Laureate. He joined the Physics Department to continue his work on the fundamental description of materials.

## Education

Ph.D. in Theoretical Condensed Matter Physics, Brandeis University (1982)

## Research Interests

- Multiple Scattering Theory: This theory describes the behavior of electrons in a metal on the basis of how an electron scatters from single isolated potentials that represent each of the atoms in the material. It is the most local treatment of the electron problem and therefore the best suited to solution on large-scale parallel computers. It is also a very challenging theory that requires complex implementation.
- Advance Statistical Methods: Systems naturally move toward lower energy and more disorder. They move toward disorder because the number of disordered states is large compared to ordered states. The measure of disorder is the entropy. The importance of disorder increases with temperature. At a phase transition, for example melting of a solid, the entropy and energy are of equal significance. Advanced statistical methods are needed to approximately count the number of states with a given energy in order to determine the entropy so that together the energy and entropy can be used to explain phase transition.
- Density Functional Theory of Electrons: This theory is the basis of the modern description of materials. It uses solutions of the Schrodinger or Dirac equations for single electrons moving in an effective potential chosen to approximate the energy of the interacting electron system. This approach has been very successful, however, significant practical limitations and fundamental questions remain. He is working on an approach that focuses on the pair correlation in the electron fluid.
- Classical Density Functional Theory: He is extending Classical Density Functional Theory to discover simple relationships between the entropy and pair correlation. The needed input, pair correlation my come from either experiment or simulation.
- Magnetic properties of Metals: He is interested in the influence of electron spin on the dynamics and thermodynamics of magnetic materials. The effect of very large magnetic fields on materials is particularly interesting and underexplored.
- Combined molecular and spin dynamics in magnetic materials: He is working on computer codes that moves the atoms based on Newton’s equations of motion and rotates the orientation of atomic level magnetic moments according to the Landau-Lifshitz equation. This work is important for understanding the properties of bulk materials and spintronics.
- Metallic Glasses: When most liquid metal alloys are cooled they crystalize; metallic glasses are those that don’t crystallize but instead become a frozen liquid, i.e., a glass. The atomic dynamics near the glass transition is poorly understood. I use a variety of tools to study this regime.
- Atomic Level Stress: In materials near zero temperature the forces on all atoms are zero; we know this because they are not accelerating. However, stresses at the atomic level can be very large. He is developing first principles approaches to the atomic level stress in hopes that this stress can be correlated with and help explain measured and simulated behavior.
- Defects in metals: When a material is subjected to forces, radiation, or chemical attack, it is the defects that redistribute energy and stress. The defects determine whether or not a material fails. He is using large scale computing to study the properties of defects in metals.
- Magneto Caloric Effect: When some materials are moved into a magnetic field they become hotter. This effect can be used to pump heat out of a building, i.e., air-conditioning. Magnetic based cooling has the potential to outperform conventional air-conditioning that is based on compressing a gas to make it hotter. He is using first principles techniques to study these metals.

## Publications 2015-2021

Entropy Pair Functional Theory: Direct Entropy Evaluation Spanning Phase Transitions. D. M. Nicholson, C. Y. Gao, M. T. McDonnell, C. C. Sluss, D. J. Keffer. *Entropy* **23**, 234. (2021).

Electronic structure and atomic level complexity in AlTiZrPdCuNi high-entropy alloy in glass phase, Kh. Odbadrakh, L. Enkhtor, Ts. Amartaivan, D. M. Nicholson, G. M. Stocks, and T. Egami *Journal of Applied Physics* **126**, 095104 (2019).

Collective dynamics in atomistic models with coupled translational and spin degrees of freedom Dilina Perera, Don M. Nicholson, Markus Eisenbach, G. Malcolm Stocks, and David P. Landau *Phys. Rev. B* **95**, 014431, (2017).

Decisive role of magnetism in the interaction of chromium and nickel solute atoms with 1/2〈111〉-screw dislocation core in body-centered cubic iron. Kh. Odbadrakh, G. Samolyuk, D. Nicholson, Y. Osetsky, R.E. Stoller, G.M. Stocks, *Acta Mat.* **121**, 137-143, (2016).

Magnitude of the Wang-Landau error. Gregory Brown, PA Rikvold, Kh Odbadrakh and DM Nicholson, *J. Phys.: Conf. Ser. ***750** 012015, 29th Workshop on Recent Developments in Computer Simulation Studies in Condensed Matter Physics 22–26 Georgia, (2016).

Reinventing atomistic magnetic simulations with spin-orbit coupling, Dilina Perera, Markus Eisenbach, Don M. Nicholson, G. Malcolm Stocks, and David P. Landau *Phys. Rev. B* **93**, 060402, (2016).

Iron-based composition for magnetocaloric effect (MCE) applications and method of making a single crystal, Boyd McCutchen Evans III, Roger A Kisner, Gail Mackiewicz Ludtka, Gerard Michael Ludtka, Alexander M Melin, Donald M Nicholson, Chad M Parish, Rios Orlando, Athena S Sefat, David L West, John B Wilgen, Patent number 9,255,343 (2016).

Reformulation of density functional theory for N-representable densities and the resolution of the v-representability problem, A. Gonis, X.-G. Zhang, M. Däne, G.M. Stocks, D.M. Nicholson, *Journal of Physics and Chemistry of Solids*, **89**, 23-31, (2016).

Magnetic field annealing for improved creep resistance. Michael P Brady, Gail M Ludtka, Gerard M Ludtka, Govindarajan Muralidharan, Don M Nicholson, Rios Orlando, Yukinori Yamamoto, Patent number, 9217187 (2015).

Alignment of iron nanoparticles in a magnetic field due to shape anisotropy, B. Radhakrishnan, D.M. Nicholson, M. Eisenbach, C. Parish, G.M. Ludtka, O. Rios, *Journal of Magnetism and Magnetic Materials, ***394**, 481-490, (2015).

Local Electronic Effects and Irradiation Resistance in High-Entropy Alloys. Egami, T., Ojha, M., Khorgolkhuu, O., Nicholson DM, *JOM* **67**, 2345–2349 (2015).

Solving the self-interaction problem in Kohn–Sham density functional theory: Application to atoms. M Däne, A Gonis, DM Nicholson, GM Stocks - *Journal of Physics and Chemistry of Solids*, **79** 55-65, (2015).