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AMBER Archive (2008)Subject: AMBER: dihedral potential with odd periodicity
From: Germain Vallverdu (germain.vallverdu_at_lcp.u-psud.fr)
Hello I am trying to do a force field for a non standard residue. I computed new charges, create new atoms type ect ... Now I would like to fit dihedral potential on my QM calculations. Then I tried to fit with a sum of AMBER dihedral potentiel function like : Etors = Vn / N * [1 + cos( n * phi - gamma ) ] My problem comes with n. If I choose n=1 or 3, when phi moves from 0 to 180° Etors remains equal at Vn . If I choose n=2 or 4 it works correctly. I tried to change hybridation of carbon but this do nothing. I tried also with CT type for carbon and this do nothing. I did tests on ethene and I join the results on the zip file. There is frcmod topology tleap procedure and results. I use AMBER 9. Thanks Germain --
Germain Vallverdu Laboratoire de Chimie Physique Université Paris Sud 11 germain.vallverdu@lcp.u-psud.fr 01 69 15 30 38 / 06 88 59 08 87 Chacun de nous a son étoile. Suivons la en nous félicitant de la voir chaque jour un peu plus loin ! (V. Grignard)
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