AMBER Archive (2000)

Subject: (no subject)

From: Alessandra Ricca (ricca_at_pegasus.arc.nasa.gov)
Date: Tue Nov 14 2000 - 17:12:00 CST

Dear Amber users,

I have been running Gibbs for imidazole in water. I get identical
forward and reverse F_energy values which I thought should be of opposite sign.
I did not use the IDWIDE option to turn off the double-wide
sampling.
My input is the following:

-------
 imidazole in h20; shake; CORC; no electrost. decoupling; dyn mod wind 1->0
 &cntrl
  irest = 0, ntx = 7,
  NSTLIM = -1, DT = 0.001,
  NTB = 2, NTP = 1, NPSCAL = 1,
  CUT = 8.0, NSNB = 25, SCEE = 1.2, IDIEL = 1, DIELC=1.0,
  NTC = 3, NTF = 3, TOL = .00001,

  NTPR = 10,

  NCORC = 1, IELPER = 0,
  ISLDYN = -2, ALMDA = 1.0,
  NSTMEQ = 1000, NSTMUL = 1000,
  DLMIN =0.1d-9, DLMAX = 0.05,
 &end
-----------------------------------

Here is the end of the output:

 nb-update: total= 162999 hbpair= 70548 pert= 4266
 NO DYNAMICALLY MODIFIED WINDOWS COLLECTED SINCE LAST REPORT

 NSTEP =1766860 TIME(PS) =1766.860 TEMP(K) = 314.101 PRESS = 7.054
 Etotal = -3967.66755 Kinetic = 966.22876 Potential = -4933.89631
 Bond = 0.00000 Angle = 21.45533 Dihed = 0.99531
 1-4 VdW = 0.13262 1-4 Elec= -18.39581 Van d Waal = 757.37148
 Elect. = -5695.45525 H-bond = 0.00000 Constraint = 0.00000
 Ekcmt = 482.15438 VirT = 479.76242 Volume = 15704.68681
                                                 Density = 0.98402

 Current Lambda = 0.999900
 Last F.E. update: Lambda = 0.999900 Step = 1764740 Method = F.E.P.
 Accumulated "forward" quantities (Regular)
    Lam+d_lam = 0.999900 F_energy = 1340.30551
 Accumulated "reverse" quantities (Regular)
    Lam-d_lam = 0.999900 F_energy = 1340.30551
    (Note: values are unchanged from last report)

Also the value of the F_energy is very large for the beginning of the
calculation. Is this normal ? The charges come from mp2/6-31G*.
No electrostatic decoupling is used. The perturb. charges used are the
same as the atomic charges from ab initio.

thanks,

Alessandra