Structure and thermochemistry of K2Rb, KRb2, and K2Rb2

The formation and interaction of ultracold polar molecules is a topic of active research. Understanding possible reaction paths and molecular combinations requires accurate studies of the fragment and product energetics. We have calculated accurate gradient optimized ground-state structures and zero-point corrected atomization energies for the trimers and tetramers formed by the reaction of KRb with KRb and corresponding isolated atoms. The K2Rb and KRb2 trimers are found to have global minima at the C2v configuration with atomization energies of 6065 and 5931 cm-1 while the tetramer is found to have two stable planar structures, of D2h and Cs symmetry, which have atomization energies of 11131 cm-1 and 11133 cm-1, respectively. We have calculated the minimum energy reaction path for the reaction KRb + KRb to K2 + Rb2 and found it to be barrierless.