Hi Marco. If I correctly understood, if you want to relax *only* some of yours atoms, you should impose some constrains in the ATOMIC_POSITIONS
http://www.quantum-espresso.org/wp-content/uploads/Doc/INPUT_PW.html#idm140629872010784 see if_pos(1), if_pos(2), if_pos(3) INTEGER Default: 1 component i of the force for this atom is multiplied by if_pos(i), which must be either 0 or 1. Used to keep selected atoms and/or selected components fixed in MD dynamics or structural optimization run. With crystal_sg atomic coordinates the constraints are copied in all equivalent atoms. Example: ATOMIC_POSITIONS (ang) Si 0.25 0.25 0.25 0 0 0 --> this will not move Si 0.0 0.0 0.0 1 1 1 --> this will move Federico IORI Marie Curie Fellow Laboratoire de Physique des Solides Bâtiment 510 - Rue André Rivière 91400 Orsay ----- Mensaje original ----- De: "Marco Di Gennaro" <[email protected]> Para: "pw forum" <[email protected]> Enviados: Miércoles, 24 de Mayo 2017 17:45:45 Asunto: [Pw_forum] Relax Linear chain with constraint Dear PW users, I would like to relax my system while keeping some geometry constraints. Specifically, I have a linear chain composed of N atoms (say A,B,C). I want to know if it is possible to relax the distance among atoms only (so AB, BC and CA) while making sure that the system stays linear after the relaxation. Following the PW doc: http://www.quantum-espresso.org/wp-content/uploads/Doc/pw_user_guide/node11.html I have tried with calculation='relax' and add namelist &IONS, but it looks like there is no relaxation at all. Thank you, Marco Di Gennaro , Dr. Nccr MARVEL - University of Basel Phone +41 61 267 3846 Klingelbergstrasse 80, Office 5.10 _______________________________________________ Pw_forum mailing list [email protected] http://pwscf.org/mailman/listinfo/pw_forum
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