Chemistry Reference
In-Depth Information
TABLE 4.3
Structural Parameters for the Octahedral Al(H
2
O)
3+
and Trigonal
Bipyramidal Al(OH)(H
2
O)
2+
Species Obtained from First Principles
Calculations Performed in Water Using a COSMO and from CPMD
Simulations in Aqueous Solution
Al(H
2
O
6
)
3+
R
(Al-OH
2
) (Å)
R
(HO-H) (Å)
θ
(HOH) (°)
B3LYP Calculations
1.96
0.97
106.6
CPMD Simulations
1.95.±.0.03
0.99.±.0.02
105.6.±.0.3
Al(OH)(H
2
O)
2+
R
(Al-O) (Å)
R
(Al-OH
2
) (Å)
R
(HO-H) (Å)
θ
(HOH) (°)
B3LYP Calculations
1.81
1.98
0.97
106.62
CPMD Simulations
1.79.±.0.01
1.98.±.0.02
1.01.±.0.03
106.16.±.0.04
Al(OH)
2
(H
2
O)
4+
r
(Al-Al)
r
(Al-OH)
r
(Al-OH
2
)
θ
(Al-O-Al)
θ
(HO
2
-Al-OH)
B3LYP Calculations
3.08
1.83
1.97
101.2
88.34
CPMD Simulations
3.05.±.0.12
1.85.±.0.03
1.95.±.0.02
103.22.±.3.68
89.49.±.6.71
structure. loses. neutral. water. molecules. via. substitution. and. that. water. exchange.
reactions. occur. that. drive. the. formation. of. Al
2
(OH)
2
(H
2
O)
4+
. species.. To. study. the.
dimerization.of.Al.ions.at.pH.values.of.3-7,.we.performed.separate.CPMD.simula-
tions.in.water.with.two.Al(OH)(H
2
O)
2+
.complexes.in.a.trigonal.bipyramidal.conigu-
ration.for.which.the.initial.geometries.were.taken.from.our.CPMD.simulations.as.
described.above.
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