Hu, H; Yang, W, *Dual-topology/dual-coordinate free-energy simulation using QM/MM force field.*,
Journal of Chemical Physics, vol. 123 no. 4
(July, 2005),
pp. 041102 [16095339], [doi] .
**Abstract:**

*We have developed a dual-topology/dual-coordinate free-energy simulation method for use with a QM/MM force field. By combining two parallel processes into one alchemical process, we are able to compute the double free-energy difference (delta deltaF) within a single simulation, which eliminates half of the expensive quantum-mechanical simulation in general. The method has been tested in computing the solvation free-energy differences of several molecular pairs and shows close agreement with experimental results.*