Bugs item #1598349, was opened at 2006-11-17 07:22
Message generated for change (Comment added) made by hansonr
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Category: File Input/Output
Group: v10.9
>Status: Closed
>Resolution: Wont Fix
Priority: 5
Private: No
Submitted By: Noel O\'Boyle (baoilleach)
Assigned to: Miguel (migueljmol)
Summary: Gaussian Cube File incorrect units

Initial Comment:
Hello Miguel, Bob,

I am trying to visualise isosurfaces of cube files which I have generated 
myself.

Jmol's cube file reader assumes that the cube file units are in Bohrs. However, 
this is only true if the 'number of points' is a negative value. Otherwise, the 
units are Angstroms (this applies to the units of the origin, as well as the 
units of the spacing).

This is described briefly at 
http://local.wasp.uwa.edu.au/~pbourke/dataformats/cube/:
"""
If the sign of the number of voxels in a dimension is positive then the units 
are Angstroms, if negative then Bohr.
"""

I think the behavior is undefined if some of the signs of the 'number of 
voxels' are positive and some are negative (i.e. what units should be used for 
the origin in that case?).

I would very much appreciate if you could fix this.

Regards,
    Noel


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>Comment By: Bob Hanson (hansonr)
Date: 2006-11-30 14:37

Message:
Logged In: YES 
user_id=1082841
Originator: NO

Noel, 

Ah, yes. Quite a long history this issue has. I'm sorry, but that page you
reference has an error. Somehow, somewhere along the way this specification
was changed, and Gaussian Cube files -- despite the clear indication that
only a negative count should indicate Bohr -- are all in Bohr, even with
the count positive.

Evidence of this is given in the code at
http://ftp.ccl.net/cca/software/SOURCES/C/scarecrow/gcube2plt.c
which reads the files as Bohr even with N > 0. 

I understand your pain. If you are trying to read the file just for its
atom coordinates, you are out of luck; if you are reading the file
specifically for its surface and you can get the coordinates from another
file, try the "angstroms" isosurface option.

Bob Hanson

Bob



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