1) First, optimize the geometry with
xyz PM7 ef scfcrt=3D1.d-10 UHF CHARGE=3D2 Quintet BONDS A= UX &
gnorm=3D0.1 let ddmin=3D0.
DUMMY lin= e

Note: be sure there are 3 lines of text before t= he 'Fe" card

2: Carve a new input from th= e associated ".arc" file

3: Add solvent = parameters to second line and re-optimize.

4: Redo= 2 and add thermo info to second line and remove "ef" from line 1= .

John

On Fri, Sep 19, 201= 4 at 7:11 AM, Henrique C. S. Junior henriquecsj^^^gmail.com wrote:
=
The same happens with ORCA as well.
= =C2=A0
---
Henrique C. S. Junior
Centro de Processamento de Dados - PMP

On Wednesday, S= eptember 17, 2014 12:27 PM, "Henrique Castro Silva Junior henriquecsj|= ,|gmail.com" <ow= ner-chemistry*ccl.net> = wrote:

Sent to CCL by: "Henrique= Castro Silva Junior" [henriquecsj**gmail.com]
Hi, I am an undergraduate in Chemistry from = Brazil, writing my thesis as
MO) descriptions that takes place in [Fe= (OH2)6]2+ --> [Fe(OH2)6]3+,
mostly using computational chemistry sof= twares.
I have decided to use MOPAC2012 and Gabedit (as a GUI), but Im h= aving
problems in getting realistic values. Here is my input:

* = =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D
* Input file for Mopac
* =3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
PM= 7 THERMO ROT=3D1=C2=A0 EPS=3D78.39 RSOLV=3D1.3 UHF CHARGE=3D2 Quintet=C2=A0= BONDS AUX
Mopac file generated by Gabedit
Fe=C2=A0 -0.1136=C2=A0 1 = -0.9091=C2=A0 1 0.0000=C2=A0 1
O=C2=A0 -0.1136=C2=A0 1 0.9109=C2=A0 1 0.= 0000=C2=A0 1
H=C2=A0 0.5055=C2=A0 1 1.2122=C2=A0 1 -0.7127=C2=A0 1
O= =C2=A0 1.7064=C2=A0 1 -0.9091=C2=A0 1 0.0000=C2=A0 1
H=C2=A0 2.0628=C2=A0 1 -1.3124=C2=A0 1 0.8307=C2=A0 1
O=C2=A0 -0.1= 136=C2=A0 1 -0.9091=C2=A0 1 -1.8200=C2=A0 1
H=C2=A0 -0.4817=C2=A0 1 -1.7= 682=C2=A0 1 -2.1477=C2=A0 1
O=C2=A0 -0.1136=C2=A0 1 -2.7291=C2=A0 1 0.00= 00=C2=A0 1
H=C2=A0 -0.8413=C2=A0 1 -3.0457=C2=A0 1 0.5936=C2=A0 1
O= =C2=A0 -1.9336=C2=A0 1 -0.9091=C2=A0 1 0.0000=C2=A0 1
H=C2=A0 -2.2569=C2= =A0 1 -1.5900=C2=A0 1 -0.6429=C2=A0 1
O=C2=A0 -0.1136=C2=A0 1 -0.9091=C2= =A0 1 1.8200=C2=A0 1
H=C2=A0 -1.0440=C2=A0 1 -0.9414=C2=A0 1 2.1566=C2= =A0 1
H=C2=A0 -2.2613=C2=A0 1 -0.0487=C2=A0 1 -0.3649=C2=A0 1
H=C2=A0= 0.7122=C2=A0 1 -3.0886=C2=A0 1 0.4108=C2=A0 1
H=C2=A0 -0.7542=C2=A0 1 -= 0.2257=C2=A0 1 -2.1427=C2=A0 1
H=C2=A0 2.0192=C2=A0 1 -1.5032=C2=A0 1 -0= .7289=C2=A0 1
H=C2=A0 0.3089=C2=A0 1 -1.7285=C2=A0 1 2.1807=C2=A0 1
H= =C2=A0 0.3233=C2=A0 1 1.2180=C2=A0 1 0.8341=C2=A0 1

The result is th= is:

** GRADIENT IS TOO LARGE TO ALLOW FORCE MATRIX TO BE CALCULATED,
(LIMIT=3D10) **
USING 'TS' OR OTHER GEOMETRY OPT= IMIZER

If I add the keyword LET the calculation goes on, returning t= his:
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 HEAT OF FORMATION =3D=C2=A0 =C2= =A0 -39.019942 KCALS/MOLE

With bond distance of ~1,82 A (much less = than what is expected, right?).
Then, I tried to perform an optimization= first, to reduce the gradient
and do not use LET:
PM7 XYZ=C2=A0 EPS= =3D78.39 RSOLV=3D1.3 UHF CHARGE=3D2 Quintet=C2=A0 BONDS AUX

The resu= lt is a fragmentation, [Fe(OH)6] + 6H and the same result (the
fragment= ation) goes with Gaussian09.
Any help will be very much appreciated and = Im sorry if Im making some
obvious and stupid mistake here, but most of= my knowledge on
computational chemistry Ive learned by myself.

=

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