The specification for H5MD 1.0.0 is released. It can be found on the project homepage http://nongnu.org/h5md/ and is presented in a journal paper in Comp. Phys. Comm.
As of now, the specification draft of H5MD is available on the project homepage http://nongnu.org/h5md/ and the mailing list h5md-user is setup.
H5MD is a file format specification to store molecular data.