Hello
all,
Please, how can I construct mixed Cartesian and Internal
Coordinates? Is there any way to construct it where variables in cartesian
coordinates do not related with one in internal coordinates. I want to do
two things, First: optimization of a system H2-Fe(OH)3, second: calculation of
Molecular orbital coefficients to get wave function of the system.
I have
this example but not well clear:
****************
It is
also possible to use both internal and Cartesian coordinates within the same
Z-matrix, as in this example:
O 0 xo
0. zo
C 0 0. yc 0.
C 0 0.
-yc 0.
N 0 xn 0. 0.
H 2 r1
3 a1 1 b1
H 2 r2 3 a2 1 b2
H 3 r1
2 a1 1 -b1
H 3 r2 2 a2 1 -b2
H 4 r3
2 a3 3 d3
Variables:
xo
-1.
zo 0.
yc 1.
xn
1.
r1 1.08
r2 1.08
r3
1.02
a1 125.
a2 125.
d3
160.
b1 90.
b2 -90.
This
Z-matrix has several features worth noting:
The variable names for the Cartesian
coordinates are given symbolically in the same manner as for internal coordinate
variables.
The
integer 0 after the atomic symbol indicates symbolic Cartesian coordinates to
follow.
Cartesian coordinates can be related by a sign change just as dihedral
angles can.
*************************
Finally, in this article ( H. B.
Schlegel, Int. J. Quant. Chem. Symp. 26, 243 (1992
mixed internal and Cartesian coordinates were shown to have some
advantages for some cases.
Regards
for all
Safiya
Amer
Graduate Student
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h2feoh3||gmail.com