https://www.ks.uiuc.edu/Research/namd/mailing_list/namd-l.2013-2014/0233.html
namd-l: colvar keyword ForceNoPBC
namdlkeyword
https://www.ks.uiuc.edu/Research/namd/mailing_list/namd-l.2013-2014/0234.html
namd-l: Re: colvar keyword ForceNoPBC
namdlkeyword