Abstract
The deviation of the electron density around the nuclei from spherical symmetry determines the electric field gradient (EFG), which can be measured by various types of spectroscopy. Nuclear Quadrupole Resonance (NQR) is particularly sensitive to the EFG. The EFGs, and by implication NQR frequencies, vary dramatically across materials. Consequently, searching for NQR spectral lines in previously uninvestigated materials represents a major challenge. Calculated EFGs can significantly aid at the search’s inception. To facilitate this task, we have applied high-throughput density functional theory calculations to predict EFGs for 15187 materials in the JARVIS-DFT database. This database, which will include EFG as a standard entry, is continuously increasing. Given the large scope of the database, it is impractical to verify each calculation. However, we assess accuracy by singling out cases for which reliable experimental information is readily available and compare them to the calculations. We further present a statistical analysis of the results. The database and tools associated with our work are made publicly available by JARVIS-DFT (https://www.ctcms.nist.gov/~knc6/JVASP.html) and NIST-JARVIS API (http://jarvis.nist.gov/).
Highlights
Background & SummaryNuclear resonance spectroscopies, such as Nuclear Magnetic Resonance (NMR)[1,2] and Nuclear Quadrupole Resonance (NQR)[3] are extremely valuable as sensitive probes of the local electronic structure in solids
Shifts of the NMR/NQR spectral lines yield information of uniform susceptibilities, while their relaxation time informs about the local susceptibility at a nucleus
The difference between NMR and NQR is that in NMR, the separation of the nuclear levels is predominantly affected through external or internal magnetic fields, while in NQR it comes from the interaction of the nuclear quadrupolar moment with the gradients of the static electric field at the nucleus (Electric Field Gradients, electric field gradient (EFG))
Summary
Nuclear resonance spectroscopies, such as Nuclear Magnetic Resonance (NMR)[1,2] and Nuclear Quadrupole Resonance (NQR)[3] are extremely valuable as sensitive probes of the local electronic structure in solids. They are considered to be the golden standard in addressing such disparate physical properties of materials such as magnetism, charge ordering, structural distortion, valence skipping, superconductivity, and many others. Nuclei with a non-zero spin are NMR-active, and often the experiments require high-field magnets and cumbersome equipment. It is for this latter reason that NQR, not NMR, is used for the detection of explosives. We shall discuss the general statistical distribution of the EFG parameters
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