New kind of structure input -- constant-volume variable-cell - no sig * Using the option UseStructFile, the structural information will be read from SiestaLabel.STRUCT_IN. This option is incompatible with UseSaveXV, and will prevail.
* Siesta now always produces a SiestaLabel.STRUCT_OUT file.
The .STRUCT_XX files have the cell vectors in Ang and the atomic positions in atomic coordinates.
* The option MD.ConstantVolume will result in a constant-volume variable-cell simulation (i.e., only the cell shape and the atomic positions change).
* After every MD or relaxation step, Siesta now writes the "enthalpy" E+pV, where p is actually the target pressure.
* New tests: var_cell and constant_volume.
* Changed si test to use the new UseStructFile feature.