[AMBER] Error while running finddgref.py script

From: Akhil Sudarsan via AMBER <amber.ambermd.org>
Date: Tue, 31 Jan 2023 17:23:38 +0100

Dear AMBER users,

I am trying to find the relative energies of the protonation states of my model system using the finddgref.py tool to add it to the list of titratable residues. The system I am using is an ionizable lipid. However when I try to execute the finddgref.py script, I can see that the value of the number of steps (nstlim) gets reduced from 10,00,000 in the md.mdin file to 50 in the md.mdin.temporary file. This results in a blank cpout file and I do not get any information of the relative energies. The template for the md.mdin input file was taken from the constant pH simulation tutorial in the AMBER website (https://ambermd.org/tutorials/advanced/tutorial18/section3.htm). How can I fix this?

Log file:
 Checking cpin file and/or cein file.
 We are going to find DELTAGREF for a pH titratable residue without using Replica Exchange.
 The solvent pH value is 9.470 and was loaded from the mdin file (md.mdin).
 The temperature is 300.00 K and was loaded from the mdin file (md.mdin).
 According to the mdin file (md.mdin), the value of ntcnstph is 5.
 According to the mdin file (md.mdin), the value of nstlim is 1000000.

 The program will try to find a range of values for DELTAGREF automatically, as the argument -dgrefrange was not given

 AMBER execution #1: running 50 MD steps for DELTAGREF = 0.000000 kcal/mol

ERROR: Could not read the fraction of protonated or reduced species from the output of cphstats or cestats. The command executed was:

       cphstats -i mc3h-head1.cpin.temporary mc3h.cpout

       The execution of finddgref.py stopped

Best Regards,
Akhil Sudarsan

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Received on Tue Jan 31 2023 - 08:30:02 PST
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