For each constant of a (a1-a5), you should only have one number.
If I remember correctly, this happens when you do not use 5 points.
In other words, you must have only 5 case_coa___*.scf files in your case
directory. Keep the five case_coa___*.scf files closest to the minimum.
Move (or delete) the other case_coa___*.scf files. Then, plot E vs. c/a
again.
[http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg05826.html]
On 1/24/2014 7:29 PM, Lawal Mohammed wrote:
Dear Gavin Abo, Sir,
In line with the discussion above, I got when I plot E vs c/a the
following
Fit of: E = a1 + a2*x + a3*x^2 + a4*x^3 + a5*x^4
a11.000
a20.000 1.000
a3 -0.761 -0.0001.000
a4 -0.000 -0.930 0.000 1.000
a5 0.6420.000 -0.972-0.000 1.000
In this case what should be the value for a2, a3, a4, and a5?
Thank you in advance for your response.
With kind regards
Mohammed Lawal
On Friday, January 24, 2014 7:08 AM, Gavin Abo <gs...@crimson.ua.edu>
wrote:
Below is a summary of previous posts that should help.
To plot energy vs b/a:
(a) You should be able to rename the scf files and then plot with the
energy vs c/a option of eplot
[http://zeus.theochem.tuwien.ac.at/pipermail/wien/2009-January/012053.html].
(b) You could also plot energy vs b/a in another program like Origin
[http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg08841.html].
To get the optimized c/a (or b/a) value, you can calculate it from
the curve fit equation
[http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg05826.html].
An example calculation is given below.
When you plot E vs. c/a with eplot, you should get something like:
Fit of: E = a1 + a2*x + a3*x^2 + a4*x^3 + a5*x^4
a1 = -2201.24
a2 = 0.00233422
a3 = 0.000188276
a4 = 1.33462e-05
a5 = 9.76521e-07
From dE/dx = 0, we get the equation:
a2 + 2*a3*x+3*a4*x^2+4*a5*x^3 = 0
Solving this equation for x, x = -7.7555, which is the optimized c/a
ratio in %. I got x with Octave, but there are other software
programs that you can find on the internet to solve the polynomial
equation.
Octave input:
dEdx = [4*9.76521e-07,3*1.33462e-05,2*0.000188276,0.00233422]
roots(dEdx)
Octave output:
-1.2474 + 8.6889i
-1.2474 - 8.6889i
-7.7555 + 0.0000i <= This polynomial root is chosen as x, because
the imaginary part is zero and it appears in the energy vs c/a plot.
If you also want the minimum E, just plug the x value back into the
curve fit equation and solve for E (= -2201.2495).
On 1/22/2014 7:22 AM, MAHDI SALMANI HIRMAND wrote:
Dear Prof. Blaha,
Please let me know why there is not a program for finding minimum of
c/a or b/a ratio with Wien2k Package when we optimize c/a or b/a.
eplot program can show curve of Energy Vs. c/a but it doesn't find
minimum of c/a.
Please guide me
With best
Mahdi
_______________________________________________
Wien mailing list
Wien@zeus.theochem.tuwien.ac.at
http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
SEARCH the MAILING-LIST at:
http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html
