The analysis of the electron density
distribution in a molecular system based on the orthonormal natural atomic orbitals.
are the occupancies of the natural atomic orbitals. These rigorously satisfy the Pauli exclusion principle
The population of an atom
is the sum of natural populations
A distinguished feature of the NPA
method is that it largely resolves the basis set
dependence problem encountered in the Mulliken population analysis method.
IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by
A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997).
XML on-line corrected version: http://goldbook.iupac.org (2006-) created by M. Nic,
J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8. https://doi.org/10.1351/goldbook