On Fri, Feb 21, 2020 at 2:26 AM Erez Tamir <[email protected]> wrote: > > Dear all, > > I'm trying to apply the relative entropy (RE) method, with LJ 12-6 > interactions, for polymer melt containing 8 bead types. > My final goal is to reproduce mechanical properties of the atomistic system > by CG potentials. > In order to obtain reasonable initial guess I used the IBI method with > pressure correction until the target density and pressure obtained. > The mechanical behavior is underestimated by the IBI potentials, so I would > like to improve them by fitting and optimizing LJ 12-6 potentials with the RE > method. > Each IBI potential was fitted by lj126 function and the obtained parameters > are the initial guess. > I understand that the lj126 functional in votca is of the form: > U(r)=(A/r^12)-(B/r^6), so A=4*ε*σ^12 and B=4*ε*σ^6. Is this correct? > Following this my RE input for example for ε=2.1Kcal/mol and σ=4.8A is: > > #xy > 0 1256533682 > 1 102737 > > The following error message appears during iterations: > > an error occurred: > Hessian NOT a positive definite! > This can be a result of poor initial guess or ill-suited CG potential > settings or poor CG sampling. > > Is this error due to incorrect input or poor initial guess? Sikandar knows the details better than me, but I believe this error usually means you didn't sample long enough in the iteration step and hence the hessian is not positive definite.
Christoph > The settings file is attached. > > Any help will be appreciated. > > Best, > Erez > > -- > You received this message because you are subscribed to the Google Groups > "votca" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/votca/aa80f59c-7712-4063-b508-8845d366dd79%40googlegroups.com. -- Christoph Junghans Web: http://www.compphys.de -- You received this message because you are subscribed to the Google Groups "votca" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/votca/CAHG27e5ZSYZXr-APH7i2U42exrRyBzU-hL%3DLYeA0VoFydmaKDg%40mail.gmail.com.
