Dear CP2K Community,I'm running QM/MM simulations where several oxygen atoms (some inside and some outside of my QM region) are exhibiting instability. I'd like to stabilize these oxygens by adding capping hydrogens "on the fly" without modifying my original structure files. Based on my reading of the documentation, the VIRTUAL_SITE functionality might be applicable, but I'm uncertain about the correct implementation. My specific questions are:<ol style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0);"><li>Is it possible to use VIRTUAL_SITE to add capping hydrogens to stabilize dangling oxygens in the QM region?</li><li>If so, what is the correct syntax? I've attempted to understand the documentation but remain unclear on:<ul><li>How to properly define the position of the virtual hydrogen relative to the oxygen</li><li>How to include this virtual site in the QM region</li><li>How to set appropriate restraints to maintain proper O-H geometry</li><li>Whether to not I have to modify the Coordinate and forcefields</li></ul></li><li>Alternatively, is there a better approach in CP2K for addressing unstable oxygens during a QM/MM simulation?</li></ol>For context, I'm using CP2K version 7.1 with a QMMM setup where the QM region is treated with DFTB3 and the MM region with AMBER force fields.Any guidance or examples would be greatly appreciated.Thank you, Ben -- You received this message because you are subscribed to the Google Groups "cp2k" group. To unsubscribe from this group and stop receiving emails from it, send an email to <a href="mailto:cp2k+unsubscribe@googlegroups.com">cp2k+unsubscribe@googlegroups.com</a>. To view this discussion visit <a href="https://groups.google.com/d/msgid/cp2k/4640dcf3-da05-4e5b-9688-c30c0b514fa2n%40googlegroups.com?utm_medium=email&utm_source=footer">https://groups.google.com/d/msgid/cp2k/4640dcf3-da05-4e5b-9688-c30c0b514fa2n%40googlegroups.com</a>.