<div dir="ltr">Hi, everyone: <div><br></div><div>I am trying to simulate the transportation of atom through a membrane, in which the <b><font color="#ff0000">scalar </font></b><font color="#ff0000">speed (mode of velocity) should be set as constant. </font></div><div>But I really do not know how to set this constant speed condition in CP2K. </div><div>If you have any idea, please give me a hand. Many thanks!</div><div><br></div><div>If this is difficult, I should also try the second best<font color="#ff0000"> as set the Velocity in a direction as constant. </font></div><div>I am wondering whether I can<font color="#0000ff"> constrain the the distance of the atom to a fixed point</font> to be increased at specific value in each time step?</div><div><br></div><div>In the following example, I <b>set a constrain </b>on <font color="#ff0000">the distance in the x direction</font> from <font color="#3d85c6">No.409 atom to the fixed point at (4, 7, 7) </font>to <font color="#ff0000"><b>increase 0.01 Angstrom with each MD step</b></font>.  </div><div><br></div><div>such as : </div><div><br></div><div><div>#-----Colvar-------</div><div>  &COLVAR</div><div>    <font color="#ff0000"><b>&Distance</b></font></div><div>    &Point</div><div>    <font color="#ff0000"> Atoms 409</font></div><div>    Type Geo_center</div><div>    &End Point</div><div>    &Point</div><div>    <font color="#ff0000"> Type Fix_point</font></div><div><font color="#ff0000">    xyz [angstrom] 4 7 7</font></div><div>    &End Point</div><div>    Points 1, 2</div><div>    Axis x</div><div>    <font color="#cc0000"> &END Distance</font></div><div><br></div><div>  &END COLVAR</div><div> &END SUBSYS</div></div><div><br></div><div><br></div><div><div> &MOTION</div><div>#===================</div><div> <font color="#0000ff">  &Constraint</font></div><div><font color="#0000ff">  &Collective<br></font></div><div><font color="#0000ff">   Colvar 1</font></div><div><font color="#0000ff">   Intermolecular</font></div><div>   Target 0</div><div>   Target_limit 25</div><div>   <font color="#0000ff"> Target_Growth 0.01</font></div><div><font color="#0000ff">  &End Collective</font></div><div>  #Constraint_init .True.<br></div><div>  &Constraint_info</div><div>   Filename = constraint.inf</div><div>  &END Constraint_info</div><div>  &END Constraint</div><div>#===================<br></div><div><font color="#0000ff">  &MD<br></font></div><div><font color="#0000ff">   ENSEMBLE NVE</font></div><div><font color="#0000ff">   STEPS 500</font></div><div><font color="#0000ff">   TIMESTEP 0.1</font></div><div> &END MD</div><div><br></div><div>But it seems do not run as I thinking. </div><div><br></div><div>Thanks for any reply, suggestion and comment. </div><div>Best regards, </div><div><br></div><div>Y. Huang                                                                                                           224,19    98%</div></div><div><br></div></div>