Forum: Forums topas RSS
Negative FWHM encountered
rowlesmr #1
Member since Oct 2011 · 245 posts
Group memberships: Members
Show profile · Link to this post
Subject: Negative FWHM encountered
Is there anyway to find out what is causing this to occur? (In TA6)

As far as I can tell,I've properly constrained everything associated with a FWHM.

I seem to recall somewhere, there was a flag to use the absolute value of FWHM. Am I wrong?
--
Matthew
rowlesmr #2
Member since Oct 2011 · 245 posts
Group memberships: Members
Show profile · Link to this post
A little debugging lead me to fix cell prms of one phase, and that solved a FWHM problem?
--
Matthew
AlanCoelho #3
Member since Aug 2011 · 323 posts
Group memberships: Members
Show profile · Link to this post
In V6 the keyword force_positive_fwhm can be used. Be careful as it modifies the meaning of your equations. IMO the cause of the negative FWHM should be identified rather than use force_positive_fwhm.
rowlesmr #4
Member since Oct 2011 · 245 posts
Group memberships: Members
Show profile · Link to this post
That's what I was trying to do. I was fixing every prm associated with a peak shape. Eventually, I fixed my cell prms, and it went away.

How is FWHM affected by peak positions?

Is there any output I can look at to show me which prms are doing what and how they lead to negative FWHM?
--
Matthew
AlanCoelho #5
Member since Aug 2011 · 323 posts
Group memberships: Members
Show profile · Link to this post
You could output the total gauss_fwhm and total lor_fwhm by getting the lor_conv and gauss_conv objects and using phase_out; ie.

      phase_out file append load out_record out_fmt out_eqn
      {
          "%4.0f " = H;
          "%4.0f " = K;
          "%4.0f " = L;
          " %9g   " = Get(lor_conv);
          " %9g\n" = Get(gauss_conv);
      }

If using pv peak types the you can simply output the pv_fwhm parameter using phase_out.

Cell parameters should have limits especially for small weight_percents.
Close Smaller – Larger + Reply to this post:
Verification code: VeriCode Please enter the word from the image into the text field below. (Type the letters only, lower case is okay.)
Smileys: :-) ;-) :-D :-p :blush: :cool: :rolleyes: :huh: :-/ <_< :-( :'( :#: :scared: 8-( :nuts: :-O
Special characters:
Go to forum
Not logged in. · Lost password · Register
This board is powered by the Unclassified NewsBoard software, 20150713-dev, © 2003-2015 by Yves Goergen
Current time: 2020-11-29, 14:20:40 (UTC +00:00)