[15] TNT refinement package

The scope of TNT is to optimize atomic coordinates with respect to a series of observations, usually diffraction data and ideal stereochemistry. It also provides information to aid in the examination and correction of the refined model. These include the difference maps to be displayed along with the model, the automatic location of peaks in these maps, and indicators of the problem spots in the refined model that should be examined directly by the crystallographer. Although TNT is an excellent package for everyday refinement, its flexibility allows it to be used as a tool for the development of new refinement techniques. The TNT components can be recorded, new components to implement the refinement of the model against a novel set of observations can be added, or other kinds of changes without having to modify the existing programs can be made. To solve any computational problem, one establishes a protocol that is based on a collection of assumptions about the nature of the problem.