This article was originally published online on 29 August 2013 with one of the funding contract numbers omitted in the “ACKNOWLEDGMENTS” section.
We thank Hua Guo for providing us with a version of the XXZLG potential and for helpful discussions. This work was supported by a grant from the U. S. Army Research Office under grant number W911NF-09-1-0199 and the Office of Basic Energy Sciences, Division of Chemical Sciences, U.S. Department of Energy under Contract No. E-AC02-06CH11357 and DE-SC0010616.
Available at: http://works.bepress.com/richard_dawes/55/