New and improved features

Multiple molecule types with identical SETTLE parameters are now supported

This can be useful when one, for instance, wants to apply position restraints to a subset of water molecules.

Periodic SCC-DFTB, GFN1-xTB and GFN2-xTB are available for CP2K QM/MM

The CP2K QM/MM interface can now generate periodic SCC-DFTB, GFN1-xTB and GFN2-xTB inputs using short-range regularized point-charge coupling with SPME electrostatics. For GFN1-xTB and GFN2-xTB CP2K should be compiled with support for the tblite interface. The user can select Gaussian Expansion of Electrostatic Potential (GEEP) for MM charges in tight-binding methods through the qmmm-cp2k-dftb-electrostatic-coupling = gauss MDP option, which requires a CP2K 2027.1 or higher, whereas the default is short-range regularized point-charge coupling qmmm-cp2k-dftb-electrostatic-coupling = point-charge. Regular DFT methods are still using GEEP (Gauss) for electrostatics.

CMAP interactions now support free energy perturbation

Energy correction map (CMAP) torsion interactions can now be perturbed between an A state and a B state using the bonded-lambdas free-energy lambda component. The A and B state CMAP grids are linearly interpolated at each lambda value, and the corresponding \(\partial H/\partial\lambda\) contribution is accumulated for BAR/TI analysis.

To use CMAP FEP, specify a B-state CMAP type in the [ cmap ] section of the topology. The type can be given as a 1-based index or as an explicit name token (e.g. GLY, PZQ) that matches the optional name field on the corresponding [ cmaptypes ] header line. When the A and B state CMAP types differ, the interaction is treated as perturbed; when they are identical (or no B-state is specified) the standard non-perturbed code path is used.