<div dir="ltr">Dear All:<div><br></div><div>I am trying to define a collective variable for proton transport in CP2K, the corresponding definition is:</div><div><br></div><p class="separator" style="text-align: center; clear: both;"><a imageanchor="1" href="https://lh3.googleusercontent.com/-7v9Jc_V_Npg/WI69I4sUHTI/AAAAAAAAA1c/q0HlQzL-oDcOCd7cIXesYEf1qKh01O30wCLcB/s1600/01.png" style="margin-left: 1em; margin-right: 1em;"><img src="https://lh3.googleusercontent.com/-7v9Jc_V_Npg/WI69I4sUHTI/AAAAAAAAA1c/q0HlQzL-oDcOCd7cIXesYEf1qKh01O30wCLcB/s400/01.png" border="0" width="400" height="75"></a></p><p class="separator" style="text-align: center; clear: both;">where f_sw is a switch function</p><p class="separator" style="text-align: center; clear: both;"><br></p><p class="separator" style="text-align: center; clear: both;"></p><p class="separator" style="text-align: center; clear: both;"><a imageanchor="1" href="https://lh3.googleusercontent.com/-rp1f4uoihe4/WI69O_q74rI/AAAAAAAAA1g/9okVX0St7YkfcQLnNndMeMpOX_8gTo6twCLcB/s1600/02.png" style="margin-left: 1em; margin-right: 1em;"><img src="https://lh3.googleusercontent.com/-rp1f4uoihe4/WI69O_q74rI/AAAAAAAAA1g/9okVX0St7YkfcQLnNndMeMpOX_8gTo6twCLcB/s320/02.png" border="0" width="320" height="25"></a>,</p><p class="separator" style="text-align: center; clear: both;"><a imageanchor="1" href="https://lh3.googleusercontent.com/-0I6Ji5dw80s/WI69Y0cM2EI/AAAAAAAAA1o/UCUhhB4nvxwN5yJuOWSvXaVgvu0FGmbdACLcB/s1600/03.png" style="margin-left: 1em; margin-right: 1em;"><img src="https://lh3.googleusercontent.com/-0I6Ji5dw80s/WI69Y0cM2EI/AAAAAAAAA1o/UCUhhB4nvxwN5yJuOWSvXaVgvu0FGmbdACLcB/s200/03.png" border="0" width="200" height="22"></a></p><p class="separator" style="text-align: center; clear: both;"><br></p><p class="separator" style="text-align: center; clear: both;"><br></p><p class="separator" style="text-align: left; clear: both;">As the equations shown, there are many terms in the expression. Then I set up the system including a single file water chain with 7 water molecules (7 oxygen atoms and 14 hydrogen atoms and 1 additional proton). I defined the collective variable in CP2K as the equations shown, and get a very long expression. When executing CP2K, it says:</p><p class="separator" style="text-align: left; clear: both;"><br></p><p class="separator" style="clear: both;"> *** WARNING in input/input_val_types.F:431 :: val_get will truncate        ***</p><p class="separator" style="clear: both;"> *** value, value beginning with                                            ***</p><p class="separator" style="clear: both;"> *** 'CV8+CV9+CV10+CV11+CV12+CV13+CV14+CV15+CV16+CV17+CV18+CV19+CV20+CV21+C ***</p><p class="separator" style="clear: both;"> *** 22+0-2*CV1' is too long for variable                                   ***</p><p class="separator" style="clear: both;"><br></p><p class="separator" style="clear: both;">I checked the code and find that there is a variable "default_string_length" in the file /src/input/input_val_types.F. I guess I could change this variable to a larger value to include my expression correctly. Then how could I increase the value of "default_string_length"? I did not find any place that this variable is defined.</p><p class="separator" style="clear: both;"><br></p><p class="separator" style="clear: both;">Thanks in advance !</p><p class="separator" style="clear: both;"><br></p><p class="separator" style="clear: both;"><br></p><p class="separator" style="clear: both;">Tao</p><p class="separator" style="text-align: center; clear: both;"><br></p><p class="separator" style="text-align: center; clear: both;"><br></p><div><br></div></div>