Reading the exported file

[Dave Moore]

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Hello,

	There are issues with recreating densities by simply using the
MOLDEN output as-is, because there are precision problems with the
basis coefficients as written by MOLPRO in the MOLDEN input file. 
Specifically, all of the coefficients are truncated after the 6th
decimal place, rather than the 6th significant digit.  This causes
artifacts in densities computed using the coefficients, particularly
when calculating difference densities.  
	For example, take th HF/6-311++G(3df,3pd) density for a Mg atom,
then rotate the basis functions by 45 degrees and subtract the
resulting density from the original.  The difference density computed
in this manner  should be zero within the precision of the
calculation (specified as 1e-8 using the appropriate MOLPRO
keywords), however the difference density that is computed looks like
a d-orbital with maximum magnitude ~1e-4.  This occurs because the
low precision of the d-orbital coefficients in the valence orbitals
(which have a negligible contribution to the diagonal density) causes
low precision in the s-d cross terms in the density matrix (which are
not negligible).  
	This problem would be avoided if the orbital coefficients were
reported to the 6th significant digit, rather than the sixth decimal
place.  It would be very useful for me to have this option when
generating MOLDEN-style output, which I use for my difference density
program.  Or if it is possible to get the coefficients output to 6
sig figs in *any* ASCII output file, that would also be a help. 
Thank you,

Dave Moore
Chemistry Dept.
University of North Carolina at Chapel Hill

- -----Original Message-----
From: owner-molprouser at tcpc3.bham.ac.uk
[mailto:owner-molprouser at tcpc3.bham.ac.uk]On Behalf Of Peter Knowles
Sent: Saturday, October 27, 2001 10:43 AM
To: John Kerkines
Cc: molpro-user at tcpc3.bham.ac.uk
Subject: Reading the exported file


I think at this point we can say definitively that the EXPORT command
should essentially be forgotten about. It was originally set up when
orbital and density records were simple dumps of the (floating-point)
numbers; now they contain lots of metadata as well, and any attempt
to
EXPORT them as floating point may well cause floating point
exceptions
on, for example, Alpha hardware.

The recommended alternative is to use the interface to the molden (
http://www.caos.kun.nl/~schaft/molden/molden.html ) code (see Molpro
manual section 12.3.1,
http://www.tc.bham.ac.uk/molpro/molpro2000.1/doc/manual/node98.html#90
25
) in which are dumped the geometry, MO coefficients and occupation
numbers. Provided that one always dumps natural orbitals, this should
be enough to reconstruct the density matrix as well.
The precision of the dumped MO coefficients has for these purposes
been
raised through patch 2000.1.molden

Peter

At Tue, 18 Sep 2001 17:57:18 +0300 (EET DST),
Ioannis Kerkines wrote:
> 
> Hello,
> 
> I have used the EXPORT card to export the orbitals of the records
> 2130.2 and 2140.2. After that, I have used the Fortran code
> specified in the manual in order to read these two exported binary
> files. I get two files (one for 2130.2 and one for 2140.2) with
> lots of numbers. Does anybody know how to read this file?
> 
> I have spotted in various places in these last files, the nuclear
> charges, the geometry, the coefficients of the basis functions in
> each molecular orbital and the MO eigenvalues. There are also lots
> of zeroes (actually there are numbers like 10**(-322) = 0 ).
> 
> In which lines are the above data located? And what about in the
> record 2140.2 when doing a state-averaged CASSCF? 
> 
> Best Regards,
> John Kerkines

- -- 
Prof. Peter J. Knowles              
Email P.J.Knowles at bham.ac.uk  Phone +44-121-414-7472  Fax
+44-121-414-7471
School of Chemical Sciences, University of Birmingham, Birmingham,
B15 2TT, UK
WWW http://www.tc.bham.ac.uk/~peterk/

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