heloo experts,
I want to study the interaction between carbon nanostructures, for that i have planned to include vdw pseudos(vdw/DRSLL). When i run single point calculations over the relax geometry obtained from GGA/PBE with that of vdw pseudos i got atomic forces more than that from my relax geometry. kindly explain why i am getting so.? Does my way of doing calculations is accurate or not. ?
Dear
what you get as results is natural behavior of DFT calculations. calculations based on pseudopotentials that use the GGA-pbe functional don't take into account the VDW interactions. so, when you run your GGA-based structure relaxation you gets forces and relaxed atomic positions. when you include the vdw interactions all things changes. so, the structure obtained by GGA is no longer the relaxed structure for vdw based DF calculations. if you would do things rightly you should create pseudopotentials that take intoacunt vdw interaction and run your calculations in the nromal way as usual or you can take the strarting structure as the the GGA structure and do additional structure relaxation to obtain the true relaxed structure.
best regards
We do not have any PP prepared for vdW functional. You can use this functional with GGA-PBE PP and you will get the good results in fact better than only using GGA calculation in vdW cases. These DF families are not correction instead they functional just like GGA, LDA. Hence you have to relax the structure with this functional and it has been quite good at predicting various properties.
sir, Can we use GGA-PBE pseudo potential for vender wall interaction ?
and which flag should we give in .fdf file for vander walls interaction?
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