Dear all, I'm currently running calculations with simple linear molecules (for example : hydrogen cyanide HCN) adsorbed on graphene+metal surface. Surprinsigly, I faced few issues concerning the relaxation of these structures. Sometimes the molecules can not relax without forming an angle around 140° instead of 180° as expected.
In order to fix this I used the CONSTRAINTs tag as shown here : CONSTRAINTS 1 1.5 'planar_angle' 33 34 35 The 33, 34 and 35 atoms being the concerned atom. Even with the constraints it is sometimes impossible to obtain a logical relaxed structures with an angle around 180°. And sometimes the calculation are even crashing with the message " g = 0 is not satified ". I have read the doc about constraints of pw.x but nothing indicates me the way to resolve this. Also I would like to understang how the parameter CONSTR_TOL (equal to 1.5 in the example) affects the calculations (nothing in the doc about this point) ? Thanks -- Julien Claudot Post-doc IGCM UMR5253 DAMP team
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