Electric field gradient

In <a href="/facts/Atomic_physics/7Jlm4I7k">atomic</a>, <a href="/facts/Molecular_physics/ArRhIjdY">molecular</a>, and <a href="/facts/Solid-state_physics/Cmc6hvyR">solid-state physics</a>, the electric field gradient (EFG) measures the rate of change of the <a href="/facts/Electric_field/tt4MooBs">electric field</a> at an <a href="/facts/Atomic_nucleus/orpIm5Xl">atomic nucleus</a> generated by the <a href="/facts/Electron/L0KBo5cW">electronic</a> <a href="/facts/Charge_distribution/xFDPXUDM">charge distribution</a> and the other nuclei. The EFG couples with the nuclear electric <a href="/facts/Quadrupole_moment/6pCeNmwT">quadrupole moment</a> of quadrupolar nuclei (those with <a href="/facts/Spin_quantum_number/5Nh2H8gr">spin quantum number</a> greater than one-half) to generate an effect which can be measured using several <a href="/facts/Spectroscopic/mj71FuNK">spectroscopic</a> methods, such as <a href="/facts/Nuclear_magnetic_resonance/pGYAn9Bz">nuclear magnetic resonance</a> (NMR), <a href="/facts/Microwave_spectroscopy/kfc6kCh8">microwave spectroscopy</a>, <a href="/facts/Electron_paramagnetic_resonance/TDHV8c9e">electron paramagnetic resonance</a> (EPR, ESR), <a href="/facts/Nuclear_quadrupole_resonance/WaWQc852">nuclear quadrupole resonance</a> (NQR), <a href="/facts/M%C3%B6ssbauer_spectroscopy/GIhmBXL6">Mössbauer spectroscopy</a> or <a href="/facts/Perturbed_angular_correlation/BE5K5ebF">perturbed angular correlation</a> (PAC). The EFG is non-zero only if the charges surrounding the nucleus violate <a href="/facts/Cubic_symmetry/qLqhYxgm">cubic symmetry</a> and therefore generate an inhomogeneous electric field at the position of the nucleus.
EFGs are highly sensitive to the <a href="/facts/Electronic_density/L5yDsk6j">electronic density</a> in the immediate vicinity of a nucleus. This is because the EFG <a href="/facts/Operator_(physics)/rCJw8UFz">operator</a> scales as r−3, where r is the distance from a nucleus. This sensitivity has been used to study effects on charge distribution resulting from substitution, <a href="/facts/Weak_interaction/f6upmKMs">weak interactions</a>, and charge transfer. Especially in <a href="/facts/Crystal/e2R2mk3E">crystals</a>, the <a href="/facts/Local_structure/GGG2UBp2">local structure</a> can be investigated with above methods using the EFG's sensitivity to local changes, like defects or <a href="/facts/Phase_transition/eLP2BY8R">phase changes</a>. In crystals the EFG is in the order of 1021V/m2. <a href="/facts/Density_functional_theory/wwz4Gqdg">Density functional theory</a> has become an important tool for methods of <a href="/facts/Nuclear_spectroscopy/wGIS5IGq">nuclear spectroscopy</a> to calculate EFGs and provide a deeper understanding of specific EFGs in crystals from measurements.

Electric field gradient open-in-new

Electric field gradient