W. J. Boettinger,1 J. A. Warren,1 C. Beckermann,2 and A. Karma3 1Metallurgy Division, Materials Science and Engineering Laboratory, NIST, Gaithersburg, Maryland 20899; e-mail: [email protected]; [email protected] 2Department of Mechanical and Industrial Engineering, University of Iowa, Iowa City, Iowa 52242; e-mail: [email protected] 3Department of Physics and Center for Inter...