NBO 6.0 : Natural bond orbital analysis program

We describe principal features of the newly released version, NBO 6.0, of the natural bond orbital analysis program, that provides novel "link-free" interactivity with host electronic structure systems, improved search algorithms and labeling conventions for a broader range of chemical species, and new analysis options that significantly extend the range of chemical applications. We sketch the motivation and implementation of program changes and describe newer analysis options with illustrative applications.