RE: MOPAC question

["Erickson, Jon" <jerickson(-(at)-)dowelanco.com>]

 The easiest solution is to do the calculation in cartesian coordinates
 with the key work: XYZ
 Try the below dat file: (it worked with our version of MOPAC6)
 nointer ef precise polar xyz
 p-tolyl acetylene
 am1 calculation
 0006 1.3981    0001 0.0000    0001 0.0000    0001 0000 0000 0000
 0006 0.6991    0001 1.2108    0001 0.0000    0001 0000 0000 0000
 0006 -0.6991   0001 1.2108    0001 0.0000    0001 0000 0000 0000
 0006 -1.3981   0001 0.0000    0001 0.0000    0001 0000 0000 0000
 0006 -0.6991   0001 -1.2108   0001 0.0000    0001 0000 0000 0000
 0006 0.6991    0001 -1.2108   0001 0.0000    0001 0000 0000 0000
 0006 2.8381    0001 0.0000    0001 0.0000    0001 0000 0000 0000
 0001 1.2419    0001 2.1510    0001 0.0000    0001 0000 0000 0000
 0001 -1.2419   0001 2.1510    0001 0.0000    0001 0000 0000 0000
 0006 -2.9231   0001 0.0000    0001 0.0000    0001 0000 0000 0000
 0001 -1.2419   0001 -2.1510   0001 0.0000    0001 0000 0000 0000
 0001 1.2419    0001 -2.1510   0001 0.0000    0001 0000 0000 0000
 0006 4.0421    0001 0.0000    0001 0.0000    0001 0000 0000 0000
 0001 -3.2812   0001 -1.0401   0001 0.0000    0001 0000 0000 0000
 0001 -3.2982   0001 0.5079    0001 0.9007    0001 0000 0000 0000
 0001 -3.2982   0001 0.5079    0001 -0.9007   0001 0000 0000 0000
 0001 5.0981    0001 0.0000    0001 0.0000    0001 0000 0000 0000
 The other option is to put dummy atoms (XX) on the 2 acetylene carbons
 perpendicular to the triple bond and define the dihedrals of the
 terminal C and H as 90 degrees the dummies.
 Hope this helps.
 Jon Erickson
 DowElanco CAMD
 >----------
 >From: 	Hr. Dr. S. Shapiro[SMTP:toukie(-(at)-)zui.unizh.ch]
 >Sent: 	Thursday, September 04, 1997 11:12 AM
 >To: 	chemistry(-(at)-)www.ccl.net
 >Subject: 	CCL:MOPAC question
 >
 >
 >
 >Dear Colleagues;
 >
 >	I would like to do a MNDO optimisation for the molecule
 >p-tolylacetylene; however, when I run MOPAC 6.0 using the Z-matrix
 >for this molecule with the keywords "nointer ef precise polar",
 the
 >calculation aborts because MOPAC rejects structures that appear to
 >have too many atoms all in a straight line [e.g., the C(ar)-C#C-H atoms are
 >aligned at 180 degrees].  I understand that MOPAC _is_ able to run this
 >calculation if Cartesian coordinates are substituted for the MOPAC Z-matrix
 >in the input.  However, I can't find any useful information about this
 >option in the MOPAC 6.0 manual (though I confess that I _may_ have
 >overlooked this information whilst going through my hard copy of the user's
 >manual).
 >
 >	Therefore, I'd be grateful to anyone who can give me detailed advice about
 >how to run a MOPAC calculation for p-tolylacetylene, with or without
 >Cartesiabn coordinates as the input.  If Cartesian coordinates _must_ be
 >used as the input, what special keywords do I need, and exactly how (for
 >example) should this Cartesian coordinate input be written?
 >
 >	Thanks in advance to all responders.
 >
 >Sincerely,
 >
 >S. Shapiro
 >toukie(-(at)-)zui.unizh.ch
 >
 >
 >
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