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[PA13808%UTKVM1.BITNET ( ( at ) ) OHSTVMA.ACS.OHIO-STATE.EDU]

 GEOMETRY OF NITROGEN MOLECULES
      A number of reports of problems with calculating the geometry of
 amines using mol mech and semiempirical and small basis set ab initio
 calc have recently been aired on the network. I would like to refer
 interested workers to a paper by Boggs and NIU. J.of COMP CHEM. vol
 SIX pages 46-55 (1985) AB initio calc of amine out of plane Angles.
 This paper shows that very large basis sets with very siffuse s and
 p functions are needed on ALL atoms to solve this problem. I would
 infer from this that one should not be too upset if one gets incorrect
 results from cruder methods which are incapable of describing the
  " delicate balance between lone pair effects and delocalization"
   These methods do have severe limitations and this is clearly one
 of them. Something we have to learn to live with, despite the apparent
 early succsses of thirty years ago by Coulson, Hameka and Stephen Mason
 and others on the hybridization of amino compounds.
    On another topic The recently raised problem of why G90 would not
 give a planar (d3h)structure even though to all intents and purposes
 the trans state   exists    and could be gotten from a calc in C3v
 symm. It looks like another case of the need for extreme accuracy
 in inputting coordinates in this program. TRY using the NOSYMM option
 and see what it gives. This is a common problem formolecules with
 tetrahedral symmetry. Using bond dist and angles as input it is
 common for the program to end in errors because of apparent loss in
 symm.This problem was discussed a few months ago on the network.
  John E. Bloor(PA13808 at UTKVM1)