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
Graduate Research
Assistant
MS K710, T-10
Theoretical Division
Los Alamos National Laboratory
Los Alamos, NM 87545
Tel: 505/665-0748
Fax: 505/665-3493
E-mail: ppetrone_at_lanl.gov
Received on Thu Feb 06 2003 - 10:48:02 PST
