Gibbs: DynamicWin and NSTMEQ?

From: Paula Petrone <ppetrone_at_atlas.lanl.gov>
Date: Thu 6 Feb 2003 11:48:02 -0700 (MST)

Hi all.

Following the Methane Tutorial I am "disappearing" Water into TIP3P water
solvent. As I change the NSTMEQ and NSTMUL parameters, the Free energy
varies completely (from the value in Literature -6 kcal) but still, the
difference between the "forward" and "backward" results are very close.
Increasing NSTMEQ and NSTMUL is affecting the convergence value!
How can I get a "reliable" result?

TIME(PS) = 0.124 NSTMEQ = 2, NSTMUL = 2 (Tutorial's input file)
F+_energy = 4.25522 F-_energy = -4.92872

TIME(PS) = 0.224 NSTMEQ = 4, NSTMUL = 4
F+_energy = 2.79379 F-_energy = -3.83911

TIME(PS) = 0.960 NSTMEQ = 20, NSTMUL = 20
F+_energy= 2.41011 F-_energy = -1.87081

TIME(PS) = 8.800 NSTMEQ = 200, NSTMUL = 200
F+_energy= 3.37690 F-_energy = -2.99427

TIME(PS) = 88.000 NSTMEQ = 2000, NSTMUL = 2000
F+_energy= 2.50790 F_energy = -2.29237

Can somebody explain what is going on?
(I include input file at the end of this email)

Any help or comment that can give some light to this problem is greatly
appreciated.

Paula

&cntrl
irest = 0, ntx = 7,
NSTLIM = -1, DT = 0.001,
NTB = 2, NTP = 1, NPSCAL = 0,
CUT = 6.0, NSNB = 50, IFTRES = 0, SCEE = 2.0, IDIEL = 1, DIELC=1.0,
NTC = 3, NTF = 3, TOL = .00001,
NTPR = 5,
NTT=5, TEMP0=300, NTP=1, TAUP=0.1
NCORC = 1, IELPER = -1,
ISLDYN = -2, ALMDA = 1.0, ALMDEL = 0.025,
NSTMEQ = (Varies) , NSTMUL = (Varies), AMXMOV =0.3, IAVDEM=20, AMXDEL= 0.0001,
ALMDL0 = 0.025, DLMIN =0.1d-9, DLMAX = 0.05, AMXRST = 3.0,
NTSD = 5,
&end

------------------------------------------------------
Paula M. Petrone