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[lammps-users] RATTLE in version 2017!
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[lammps-users] RATTLE in version 2017!

From: Hai Hoang <hhoang052@...24...>
Date: Wed, 18 Oct 2017 10:25:53 +0200

Dear all,

I have employed RATTLE method to constrain the rigid bonds in water molecules and to count the number of freedom for generating initial velocities of atoms as:

    # Fix rigid bonds
    fix shake_bond    fluid shake 1.0e-5 200 0 b 1 a 1

    # Creat the velocity
    velocity fluid create ${Temp_imp} ${Iseed_imp} mom yes rot yes dist gaussian

    # Transient duration
    timestep ${dt}
    reset_timestep 0

    fix npt_md fluid npt temp ${Temp_imp} ${Temp_imp} ${Damp_temp} iso ${Press_imp} ${Press_imp} ${Damp_press}

 If I used versions 2015, it works well, i.e. it exports the temperature at t=0 is exactly equal to ${Temp_imp}. However, with version 2017, it shows that at t=0, the temperature does not remove number of constraints in computing the temperature, i.e. temperature at t=0 is not equal ${Temp_imp}.

In addition, use of RATTLE in version 2017 is not stable, i.e. i mean that all input and script are the same, but run independently one of them has error, others are not. Such situations donot occur with version 2015.

(Note that: if use of SHAKE, all are correct with both versions 2015 and 2017)

So, anyone can tell me what changed in RATTLE of version 2015 and 2017? Or explain me what happen?