  Quantitatively accurate electronic structure calculations rely on the proper
description of electron correlation. A judicious choice of the approximate
quantum chemistry method depends upon the importance of dynamic and nondynamic
correlation, which is usually assessed by scalar measures. Existing measures of
electron correlation do not consider separately the regions of the Cartesian
space where dynamic or nondynamic correlation are most important. We introduce
real-space descriptors of dynamic and nondynamic electron correlation that
admit orbital decomposition. Integration of the local descriptors yields global
numbers that can be used to quantify dynamic and nondynamic correlation.
Illustrative examples over different chemical systems with varying electron
correlation regimes are used to demonstrate the capabilities of the local
descriptors. Since the expressions only require orbitals and occupation
numbers, they can be readily applied in the context of local correlation
methods, hybrid methods, density matrix functional theory and
fractional-occupancy density functional theory.
