Technical Abstract: This paper describes progress in the computational modeling of cellulose crystals since our 2007 report. These crystal models are needed to better understand the interactions of cotton cellulose with water, enzymes and chemical finishing agents. Previous models resulted from molecular dynamics simulation, but many of the differences between model and experiment could be revealed with much less computer time by the energy minimization technique. The deviations of our models, and those of other workers, could be described in terms of twists of both the individual molecules and the entire crystal. Other deviations described last year have been accepted by the original authors as artifacts of the modeling techniques. The present work describes the twisting of the molecules in terms of deviations from a two-fold screw-axis, and presents results from a periodic boundary calculation with quantum mechanics.