<div dir="ltr">Dear all<div>I'm trying to perform a simulation applying a harmonic constraint on a Collective variable (something like Umbrella sampling).</div><div>I tried  different keywords but, unfortunately, the value of the Collective Var does not change during the simulation.</div><div><br></div><div>My input file is below (the part concerning the constraint) can you help me to solve this problem?</div><div><br></div><div>Thanks</div><div><br></div><div>Jacopo</div><div><br></div><div><p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">&GLOBAL</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">  PREFERRED_FFT_LIBRARY FFTSG</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">  PRINT_LEVEL LOW</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">  PROGRAM CP2K</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">  PROJECT md3</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">  RUN_TYPE md</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">  #ECHO_INPUT</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">&END GLOBAL</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier; min-height: 6px;"><font size="4"><br></font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">&MOTION</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4"> &FREE_ENERGY</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">   &METADYN</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">     DO_HILLS .FALSE.</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">     &METAVAR</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">       COLVAR 1</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">       SCALE 1.</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">     &END</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">     &PRINT</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">       &COLVAR</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">          COMMON_ITERATION_LEVELS 3</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">         &EACH</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">           MD 1</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">         &END</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">       &END</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">     &END</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">   &END METADYN</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4"> &END FREE_ENERGY</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier; min-height: 6px;"><font size="4"><br></font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">&CONSTRAINT</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4"> &COLLECTIVE</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4"> INTERMOLECULAR  F</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">      TARGET [angstrom] 3.0</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">      TARGET_GROWTH [angstrom*fs^-1] 1.0</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">      TARGET_LIMIT [angstrom] 2.9</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">&RESTRAINT</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">  K=1.00</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">   &END</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4"> &END</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">  &END</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4"> &MD</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">    ENSEMBLE NVT</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">    STEPS 400</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">    TIMESTEP 0.50</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">    TEMPERATURE 298.5</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">    &THERMOSTAT</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">      TYPE NOSE</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">      REGION MASSIVE</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">      &NOSE</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">        TIMECON   [wavenumber_t] 2000</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">      &END NOSE</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">    &END THERMOSTAT</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">    &PRINT</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">      &ENERGY</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">        &EACH</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">          MD 1</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">        &END EACH</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">        FILENAME =md2.ener</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">      &END ENERGY</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">    &END PRINT</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">  &END MD</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">   &PRINT</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">    &TRAJECTORY  SILENT</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">      &EACH</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">        MD 5</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">      &END EACH</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">      FILENAME =md6.dcd</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">      FORMAT  DCD</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">    &END TRAJECTORY</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">    &VELOCITIES  OFF</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">    &END VELOCITIES</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">    &FORCES  OFF</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">    &END FORCES</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">    &RESTART</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">      &EACH</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">        MD 2</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">      &END EACH</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">      FILENAME =md2.restart</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">    &END RESTART</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">  &END PRINT</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><font size="4">&END MOTION</font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier; min-height: 6px;"><font size="4"><br></font></p>
<p style="margin-bottom: 0px; line-height: normal; font-family: Courier;"><br></p></div></div>