Subject: Re: CCL:orbitals

From: Philip Stortz <madscientist*at*wyoming.com>
Date: Wed, 28 May 2003 23:57:59 -0600

The idea of orbitals seems reasonable, but obviously there have been a lot of simplifications in the
already hugely complex programs written for ccl.  I would also argue, that the programs currently in
use as well as the parameters for each element have been aggressively tweaked to match lab results.
Clearly current ccl code has enough degrees of freedom to model nearly any thing else that's currently
modeled by  subtly changing parameters and/or code.  

CCL programs are useful tools only because of this "tweaking", though any tool is better than no tool
usually.  obviously correlation between calculation and result does not prove a theory "true",
particularly when you have feedback between experiment and model development.  also, most programs do
seem to do better on large systems, probably because of the tendency for errors to cancel each other
to some extent.

one of my favorite examples: there was a period during the late 60's and early seventies when the
length of ladies skirts very, very closely matched sunspot activity, for a whole 11 year cycle!  One
might have concluded that fashion can predict solar activity or vice versa, and developed the
appropriate predicative code, at least until the trend changed.  As i said, it seems to me that modern
ccl code could be modified for nearly any predictive activity and the constant tweaking means that it
must approach consistency with experimental results, no matter whether the original idea has any basis
in "reality" or not.  Reality is in the mind of the beholder, as long as you agree with the majority,
otherwise you still think you understand "reality", but others will think you foolish or insane.
Agreement with experimental data supports a theory, until that experimental data can no longer be
accommodated into the existing model or someone comes up with a simpler or more accurate theory (even
if more complicated, or fundamentally less "real").

Finally, as of last year (I believe it was last year, sorry i don't have a reference), fractional
electrons exist, at least in liquid helium near absolute zero, where they were able to induce i
believe at least 6 different species of charge carrier with different charge to mass ratios.  It
wouldn't surprise me if this partially explains (assuming you take the experimental observation to be
"real") Pi bonds.  And considering it's place on the periodic table (another highly useful but
imperfect tool) i'd suspect this may account for some of the problems modeling lithium compounds.  It
might even relate to superconductivity, which is observed, but still poorly understood i believe.

I only wish there were good code for inorganic crystal electronic spectrum calculations, but that's
not where most people see the money, so the code base hasn't been tweaked in that direction
extensively.  Still, i'd prefer i guide who happens to be right over no guidance at all, it provides
that "comfort" we all seek, and of course a way to shift the blame.  ("it's not my fault we wasted
billions, that was what the program said to do, blame the developers")

elewars wrote:
> 
> 2003 May 28
> 
> Are MOs physically real? This is a meaningful question only if there is some
> experiment or observation that could provide an answer _yes_ or _no_.  Is there,
> at least in principle, such an experiment or observation?
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-- 
Philip Stortz -- To be nobody but yourself when the whole world is trying its best night and day to make you everybody else is to fight the hardest battle any human being will ever fight. -- E.E. Cummings