* **Units**. Pymatgen now has a new system of managing units,
defined in pymatgen.core.units. Typical energy, length, time,
temperature and charge units are supported. Units subclass float,
which makes the usage transparent in all functions. The value that they
being are in terms of conversions between different units and addition and
subtraction of different units of the same type. Some basic quantities
like ionic radii and atomic masses are now returned in unitized forms for
easy conversion. Please see :mod:`pymatgen.core.units` and the
:doc:`examples </examples>` for a demonstration of house to use units in
pymatgen.
* **Minor backwards-incompatible change**. Structures are now sorted by
default when generating VASP input files using vaspio_set. Old behavior can
be obtained by setting sort_structure=False in the constructor. This is
typically the desired behavior and prevents the generation of large
POTCARs when atomic species are not grouped together.
* Bug fix for Molecule.substitute. Earlier algorithm was not detecting
terminal atoms properly.
* Additional conversion tools for ABINIT (by Matteo Giantomassi).