<HTML><BODY style="word-wrap: break-word; -khtml-nbsp-mode: space; -khtml-line-break: after-white-space; ">Sorry Luca I guess I didn't fully understand what you meant..<DIV><BR class="khtml-block-placeholder"></DIV><DIV>Anyway, let me just point few things:</DIV><DIV>NPT does not work with QMMM.. the QMMM stress tensor is not implemented.. anyway this is not a serious limitation..</DIV><DIV>Better equilibrate the system at MM level and than do an NVT or NVE..</DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV>If you want to go for an NVE (or NVT) QM and MM do not necessarily need to have the same setup for PBC..</DIV><DIV>You can have everything fully periodic (http://dx.doi.org/10.1021/ct6001169) or just QMMM minimum image interaction..</DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV>Within a QMMM calculation: the box in the QM section does not affect the PBC (if a decoupling is used) but only the use </DIV><DIV>of the plane wave for the Hartree and XC terms (Have a look at the QS algorithm).. </DIV><DIV>The CELL section in the MM affects electrostatic and PBC of the global system. The QMMM interaction is controlled through</DIV><DIV>the QMMM section..</DIV><DIV> </DIV><DIV>Hope this helps,</DIV><DIV>Teo</DIV><DIV><BR><DIV><DIV>On 17 Sep 2007, at 23:07, Luca wrote:</DIV><BR class="Apple-interchange-newline"><BLOCKQUOTE type="cite"><P style="margin: 0.0px 0.0px 0.0px 0.0px"><FONT face="Helvetica" size="3" style="font: 12.0px Helvetica">I do not understand when I want to simulate (NVE or NPT) MD for one QM-</FONT></P> <P style="margin: 0.0px 0.0px 0.0px 0.0px"><FONT face="Helvetica" size="3" style="font: 12.0px Helvetica">solute (ab-initio organic molecule) in MM-water in a periodic box. In</FONT></P> <P style="margin: 0.0px 0.0px 0.0px 0.0px"><FONT face="Helvetica" size="3" style="font: 12.0px Helvetica">this case I should have same cell parameters and same rules for PBC in</FONT></P> <P style="margin: 0.0px 0.0px 0.0px 0.0px"><FONT face="Helvetica" size="3" style="font: 12.0px Helvetica">both system QM and MM....</FONT></P> </BLOCKQUOTE></DIV><BR></DIV></BODY></HTML>