An Easier Way To Model Hydrate Lattices

Hydrate lattices, which are made up of networks of water molecule cages, hold promise as a storage medium for hydrogen and other chemical species. At the moment, computer modeling of these structures to search for the best storage hydrates is generally cumbersome because of the millions of potential configurations the network of hydrogen bonds can assume. Now, Pacific Northwest National Laboratory chemist Sotiris S. Xantheas and colleagues have devised an approach that greatly streamlines calculation of the most likely unit cell structures of hydrate lattices (J. Am. Chem. Soc., DOI: 10.1021/ja9011222). The PNNL group focused on a hydrate lattice family composed of unit cells made from six cages that contain 24 water molecules and two cages that contain 20 water molecules. They first eliminated higher energy configurations from the list of possible cage networks by maximizing the number of strong hydrogen bonds. With a list of 3 million structures pared down to 321, the group then computationally built up the networks of the three-dimensional lattices. The method should help researchers design other hydrate lattices and focus their energies on hydrates they want to try to make, the authors write.