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The current frontier in quantum chemistry lies at the edge of quantum Monte Carlo (QMC) methods which allow us to precisely describe electronic structures of large organic molecules. Understanding these molecules will play a major role in developing quantum dots, understanding biological processes, and developing solutions for clean energy. Of particular interest to experimentalists and theorists alike is the molecule porphyrin, a model compound and potential surrogate of molecules involved in respiration (myoglobin and hemoglobin) and photosynthesis (chlorophylls), with exquisite light-harvesting capabilities. Despite exhibiting D4h symmetry, its electronic structure remains a challenge for theoretical chemists and physicists, and provides a perfect platform for testing QMC methods.
The key ingredient for all electronic structure QMC calculations is the fermionic nodal surface -- a 3N-1 dimensional hypersurface that defines the regions of many-body space where the wave function is zero. But because exact numerical results of the nodal surfaces are computationally intractable, QMC methods have instead depended on the simple Hartree-Fock approximation method. Despite its success, this approximation injects an unknown amount of error into the calculation, since an infinitely long QMC computation will still be approximate to the nodal surfaces put into the model.
My research is both broad and specific. I plan to exactly calculate the fermion nodal surface of porphyrin. In addition, we will study different ansatz wave functions such as multi-determinant, pfaffian and pairing wave functions to unravel the different nodal topologies and their ultimate contribution to the energy of porphyrin. Thus, I plan to put computational methods in dialog with a dynamical approximation method that will improve accuracy for a myriad of future QMC calculations with minimal computational demand. Such work will provide theoretical and practical insight for many fields of research, with consequences reaching far and wide.
New Computational Approach to Electron Transport in Irregular Graphene Nanostructures, March 19, 2009, APS March, 54, #X25.00014
Efficient Electronic Transport Calculations for Arbitrarily-Shaped Graphene Devices, November 10-11, 2009, Molecular Foundry User's Meeting
Evaporative Cooling of a Photon Fluid, B. Seaman, D. Mason, M. Holland, June 5-9, 2007, APS DAMOP, 38, #R1.020
Onset of Chaos and Thermalization in a One-Dimensional Bose-Hubbard Lattice in the Mean-Field Regime, D. Mason, A. Cassidy, V. Dunko, M. Olshanii, March 5-9, 2007, APS, abstract #X32.009
Flares, Magnetic Fields, and Subsurface Vorticity: A Survey of GONG and MDI Data, D. Mason, R. Komm, F. Hill, R. Howe, D. Haber, and B.W. Hindman, The Astrophysical Journal, Volume 645, Issue 2, pp. 1543-1553
Flares, Magnetic Fields, and Subsurface Vorticity: A Survey of GONG and MDI Data, D. Mason, R. Komm, R. Howe, F. Hill, D. Haber, B. Hindman, 2006, SPD, 37, 5.06
Flares, Magnetic Fields, and Subsurface Vorticity: A Survey of GONG Data, D. Mason, R. Komm, F. Hill, & R. Howe, 2006, AAS, 207, 111.03
Thermalization in Integrable Quantum Gases, Marcos Rigol, Vladimir Yurovsky, Douglas Mason, Vanja Dunjko, and Maxim Olshanii, International Workshop on "Critical Stability", Dresden, Germany, October 16-22 2005
Thermalization in Integrable Quantum Gases, Marcos Rigol, Vladimir Yurovsky, Douglas Mason, Vanja Dunjko, and Maxim Olshanii, International Workshop on "Critical Stability", Princeton BEC Symposium, Princeton University, October 14-15 2005
Cyberspace and Orientalism: a Dialogue, D. Mason, University of Cincinnati 25th Conference on Romance Languages and Literatures, May 2005
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