Subject: (1)Koopman's Theorem and (2)BondingREAD/NEW

From: YONG HUANG <[email-masked]>
Date: Sat, 2 Dec 1995 13:39:48 -0600 (CST)

(1) Can anyone tell me whether ionization potential calculated based on
Koopman's Theorem is just the IP for vertical ionization? I suspect so because
I think what Koopman's Theorem misses is just the vibrational relaxation in the
ionic state after the electron is gone. Please correct me if I'm wrong.

(2) I use CAChe MOAPC to calculate the distances and bond orders between the 3
hydrogens of a NH3 right above the pai ring of ferulic acid (4-OH-3-OCH3-
cinnamic acid). After geometry optimization, NH3 shifts to the edge of the
pai-ring. I did this calculation in 3 ways: 1) no bonding is specified between
H's of NH3 and pai-ring; 2) 1 H of NH3 hydrogen-bonded to carbons #1,3,5 (if
the 6 C's are numbered 1 to 6); 3) 3 H's of NH3 hydrogen-bonded to C's #1,3,5,
respectively. My question is: Does the calculation take into account whether I
specified the bonding at all? It seems it doesn't. The results always show
small bond order between H's of NH3 and substituents of the ring AND EVEN
SMALLER bond order between those H's of NH3 and C's of the ring, regardless of
whether I draw hydrogen bond lines in the CAChe Editor (Graphic Interface for
MOPAC). Seems MOPAC Input doesn't have bond information. I guess specifying
bonds in Editor doesn't do anything at all. Can someone clarify this for me?

Thank you very much. I'll summarize.

Yong
[email-masked]