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From szilagyi@miat0.vein.hu Wed Jan 12 04:18:43 1994
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To: chemistry@ccl.net
Cc: szilagyi@miat0.vein.hu
Subject: METMOD1 force field
Date: Wed, 12 Jan 94 10:01:11 +0100
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Status: RO

Dear Netters,

	I am sending now, the first part of the METMOD1 force field.
Anyone can use it who has the PCMODEL V4.0. If someone has only the
MM2 (or similar force field MMX, MM+, etc.), he/she can very easy
install the additional parameters (marked with C). Do not need to 
reoptimize it.

Part I. Modelling of WCl4CR1R2 complexes

PARAM.NEW file:

-------------------------------------------------------------------------------
           MMX (1986)
             (THE PARAMETERS INDICATED WITH AN ASTERISK ARE NOT FINAL.)
         0 ATOMS INDICATE GENERALIZED PARAMETERS
             TORSIONAL PARAMETERS
                        ANGLE          V1          V2          V3

TOR           1      1- 1- 1- 1       0.200       0.270       0.093
        ---------- rest deleted ------------

Some instruction in use

	I marked with a letter C the new (additional) parameters.
Lets see the general formula of the complex:


	Cla		The structure is very close to the
     Cle |   R1		trigonal bipyramidal coordination.
	>W=Cc<		(but there some significant distortion)
     Cle |   R2
        Cla

Atom types:

	W 	tunsgten 	31
	Cle	equatorial Cl	12
	Cla	axial Cl	59
	Cc	carbene C	 2

		anything else is MMX default.

--------------------------------------------
      stuff deleted
--------------------------------------------

The average and RMS fitting error are less than 0.05 A !!
(Large and significant difference is in the W-Cla bond
length. From the ab initio calcns. it seems to be longer
then the equatorial one. In the literature we did not
find any similar effect, so at this time we did not make
any difference between these two bond lenght)

There is a possibility to manage with alpha hydrogen
coordination to metal atom. The user needs redefine
the alpha carbon and hydrogen and the carbene group will
rotate to minimise the distance between W and alpha-H.
(In this particular application it is not really important
but it will be in other systems.)

Test files:

--------------------------------------------
      stuff deleted
--------------------------------------------

Please find the rotational barriers, the precise description of the
parameter optimization in the published papers.

If you want to minimized the structures you need to retype the atoms
and if you want to display it you need to "backtype" the atoms, of
course.

If something is missing or not clear please write me

						Rob

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