> > This means that although the minimization was run in double precision, > the atomic configuration is saved in single precision (the last two > decimal places are not used). Does this mean that each time the > optimized *.gro file is re-read, it needs to optimize these last two > decimal places anew, and this makes the difference in SEVEN orders of > magnitude in the maximal force? >
to elaborate a bit on this simple answer - yes truncations in coordinate precision lead to much larger errors in the forces the reason is the .gro format has no precision in the coordinates - it is in nm and only has 3 decimal places - this is only 1% precision in angstrom - and remember bond length changes of 0.01 angstrom are significant - eg. a difference between c-c bonds of 1.54 and 1.55 - which is a signifcant energy change for a bond - hence the large change in forces youve already seen the solution to the problem - which is to ignore the .gro files!! David _______________________________________________ gmx-users mailing list gmx-users@gromacs.org http://www.gromacs.org/mailman/listinfo/gmx-users Please search the archive at http://www.gromacs.org/search before posting! Please don't post (un)subscribe requests to the list. Use the www interface or send it to [EMAIL PROTECTED] Can't post? Read http://www.gromacs.org/mailing_lists/users.php
