[gmx-users] settle with tip4p water

Lubos Vrbka shnek at tiscali.cz
Mon Jul 11 14:59:43 CEST 2005

hi guys,

during the learning how to use gromacs i encountered following 
"problem". when i look to tip4p.itp file i can see constraints defined. 
also, atoms have some order (dummy, hydrogen, hydrogen, oxygen). it is 
stated in the file that this "strange order" makes gromacs perform better.

i was wondering whether settle (since it should be more optimized) could 
perform better than constraints, but it requires (if i got it correctly) 
the order (dummy, oxygen, hydrogen, hydrogen) or (oxygen, hydrogen, 
hydrogen, dummy). then, the "strange order" is gone.

the question is, what should i use? settle (analytical constraints), or 
constraints? does the order in the itp file really matter so much?

thanks for any hint. best regards,

_ at _"

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