initial minimization solvent + ions
 &cntrl
  imin   = 1,
  maxcyc = 1000,
  ncyc   = 500,
  ntb    = 1,
  ntr    = 1,
  cut    = 10.0
 /
Hold PPAT-Ppant system fixed (change to 1-497 for HGMS/ACP-Ppant-Ser)
500.0
RES 1 161 
END
END