  Version 13 of XtalOpt, an evolutionary algorithm for crystal structure
prediction, is now available for download from the CPC program library or the
XtalOpt website, https://xtalopt.github.io. In the new version of the XtalOpt
code, a general platform for multi-objective global optimization is
implemented. This functionality is designed to facilitate the search for
(meta)stable phases of functional materials through minimization of the
enthalpy of a crystalline system coupled with the simultaneous optimization of
any desired properties that are specified by the user. The code is also able to
perform a constrained search by filtering the parent pool of structures based
on a user-specified feature, while optimizing multiple objectives. Here, we
present the implementation and various technical details, and we provide a
brief overview of additional improvements that have been introduced in the new
version of XtalOpt.
