| NSF Org: |
DMR Division Of Materials Research |
| Recipient: |
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| Initial Amendment Date: | July 2, 2014 |
| Latest Amendment Date: | May 29, 2016 |
| Award Number: | 1410639 |
| Award Instrument: | Continuing Grant |
| Program Manager: |
Daryl Hess
dhess@nsf.gov (703)292-4942 DMR Division Of Materials Research MPS Directorate for Mathematical and Physical Sciences |
| Start Date: | July 15, 2014 |
| End Date: | June 30, 2018 (Estimated) |
| Total Intended Award Amount: | $258,000.00 |
| Total Awarded Amount to Date: | $258,000.00 |
| Funds Obligated to Date: |
FY 2016 = $86,000.00 |
| History of Investigator: |
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| Recipient Sponsored Research Office: |
2601 WOLF VILLAGE WAY RALEIGH NC US 27695-0001 (919)515-2444 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
2401 Stinson Road Raleigh NC US 27695-8202 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): |
CONDENSED MATTER & MAT THEORY, CDS&E |
| Primary Program Source: |
01001415DB NSF RESEARCH & RELATED ACTIVIT |
| Program Reference Code(s): |
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| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.049 |
ABSTRACT
NON-TECHNICAL SUMMARY
This award supports theoretical and computational research on properties and behavior of interacting quantum systems. This is one of the most impactful frontiers of current condensed matter and materials physics. In particular, low-dimensional structures with sizes of the order of a nanometer (one billionth the size of a meter) with various competing interactions between the electrons and their spatial and spin degrees of freedom offer new and unprecedented opportunities for the development of new materials and devices with ultralow power consumption and ultrafast processing speeds. The key barrier that hampers the realization of this potential is our limited knowledge of how to efficiently and accurately describe, modify and control the relevant quantum mechanisms. The PI and his group will focus on high-performance computational approaches for solving the underlying fundamental equations and establish a new set of tools for analysis of quantum phenomena and for discovery of new materials made up of nanometer-sized components. The proposed methodology is based on an optimized combination of sophisticated analytical constructions, robust and effective simulation approaches, and high performance of large parallel computing platforms.
The computational developments will become a part of an open source simulation package for use by research communities at large. Inherent part of the effort will be the training of a graduate student in advanced simulation methods and the physics of nanometer-sized systems. Such training is expected to provide multiple opportunities for a future career in scientific research. The educational impact of this research will be further enhanced through expansion of the curriculum at North Carolina State University by developing a graduate computational physics course with emphasis on simulations of quantum systems and related topics with broad interest across physics, chemistry, materials and engineering disciplines.
TECHNICAL SUMMARY
This award supports computational and theoretical research focused on the development of computational quantum Monte Carlo methods for studies of low-dimensional materials. First, novel approaches for constructions of many-body pairing wave functions will be established using effective Hamiltonians with explicit inclusion of pairing effects based on pair density matrices. This will provide the key inputs for correlated trial wave function constructions in a robust and systematic manner so that electron correlations will be described consistently across varying spin-polarizations and symmetries. As a result, the quantum Monte Carlo accuracy for important quantities such as binding and dissociation energies, spin gaps, and excitations will increase very significantly when compared with mainstream electronic structure approaches. Second, quantum Monte Carlo methods for treating spins as genuine quantum variables will be developed and implemented for routine use in calculations of systems with important spin interactions. This development will break new ground in electronic structure calculations and will make studies of materials with significant spin-orbit effects and systems with non-collinear spins or topologically ordered states possible in a many-body wave function setting. The planned applications and prototypes target promising research challenges in low-dimensional and spintronic nanomaterials such as doped graphene and related systems.
The computational developments will become a part of an open source simulation package for use by research communities at large. Inherent part of the effort will be the training of a graduate student in advanced simulation methods and the physics of nanometer-sized systems. Such training is expected to provide multiple opportunities for a future career in scientific research. The educational impact of this research will be further enhanced through expansion of the curriculum at North Carolina State University by developing a graduate computational physics course with emphasis on simulations of quantum systems and related topics with broad interest across physics, chemistry, materials and engineering disciplines.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
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PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
Overarching focus of this project has been the developement and application of computational many-body methods with explicit treatment of quantum correlations for solving some of the most challenging problems posed by new nano and low-dimensional materials. For this purpose, we have employed quantum Monte Carlo (QMC) methods that represent highly effective many-body alternative to more traditional approaches. In particular we have applied the QMC apporoaches to the following challenges:
1) We calculated precise values of spin gaps in prototype spintronic material based on Vanadium-Benzene multidecker nanowires in ionized states. We concluded that they are ferromagnetic insulators and therefore cannot serve as spin valves as was expected from previous studies. It has become clear that for such purpose further chemical functionalization of these systems is necessary.
2) For non-covalently bonded complexes and nanosystems we achieved breakthrough subchemical accuracy (0.1 kcal/mol) for dissociation energies including examples of DNA-base pairs and systems with hydrogen bonds (long paper on this has been published in very highly ranked Chem. Rev. journal).
3) For the first time we calculated impact of electron correlations and spin-orbit in several molecules within explicitly correlated, spinor-based QMC, currently the only existing many-body alternative to traditional wave function methods based on expansions in determinants and one-particle bases.
4) for the 2D phosphorene cohesion, fundamental band gap and exciton bindings, we calculated benchmark accuracy estimations by QMC methods.
The key outcomes therefore include significant expansion of quantum Monte Carlo methods for studies of new classes of materials, new application areas and computational advances in treating electron spins as quantum variables. The implemented methods are available in parallelized versions within open source QWalk package (qwalk.org) for use by the communities at large. The project involved training of several graduate students in variety of electronic structure methods, supercomputing calculations, data analysis, writing and publishing research results.
Last Modified: 10/22/2018
Modified by: Lubos Mitas
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