Lawrence Berkeley National Laboratory
Recent Work
Title
THE PHOTODISSOCIATION OF FORMALDEHYDE: POTENTIAL ENERGY SURFACE FEATURES
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Author
Goddard, J.D.
Publication Date
1978-12-01
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THE
PHOTODISSOCIATION
OF
FORMALDEHYDE:
POTENTIAL
ENERGY
SURFACE
FEATURES
John
D.
Goddard
and
Henry
F.
Schaefer
III
December
1978
Prepared
for the
U.
S.
Department
of
Energy
under
Contract
W-7405-ENG-48
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LBL
-8545~
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of
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by
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LBL-8545
.
•
The
Photodissociation
of
Formaldehyde:
Potential
Energy
Surface
Features
*
John
D.
Goddard
and
Henry
F.
Schaefer
III
Department
of
Chemistry
and
Lawrence
Berkeley
Laboratory
University
of
California
Berkeley,
California
94720
*
National
Research
Council
of
Canada
Postdoctoral
Fellow.
'-
•
..;.;-
Abstract
Features
of
the
So
potential
energy
surface
of
formaldehyde
relevant
to
its
dissociation
to
molecular
products,
H2
+ CO,
to
radical
formation,
H + HCO,
and
to
rearrangement
to
hydroxycarbene,
HCOH,
have
been
studied
by
means
of
ab
initio
calculations.
A
gradient
p~ocedure
was
used
to
locate
and
to
characterize
both
equilibrium
and
transition
state
geometries.
Basis
sets
of
at
least
double
zeta
(DZ)
quality
were
employed
throughout
and
many
calculations
involved
more
flexible
basis
sets
including
polariza-
tion
functions.
Force
constants,
normal
modes
and
vibrational
frequencies
were
calculated
at
the
SCF
level
for
stationary
points
on
the
surface.
Extensive
configuration
interaction
(CI)
calcula-
tions
were
also
carried
out.
For
the
molecular
dissociation
the
energy
barrier
including
the
effects
of
polarization
functions
and,
electron
correlation
was
-1
-1
4.06
eV
(93.6
kcal
mole
,32700
cm
).
Correcting
for
changes
in
zero
point
vibrational
energy
gave
an
approximate
activation
~nergy
of
3.76
eV
(87
kcal
mole-I,
30300
cm-
l
)
with
an
estimated
error
6f
±
0.2
eV (± 5
kcal
mOle-I,
±.1700
cm-
l
).
The
energy
required
for
the
rearrangement
of
formaldehyde
to
trans-hydroxycarbene
was
-1 -1
calculated
to
be
3.85
eV
(89
kcal
mole
,31000
cm
)
at
the
DZ
+
polarization
+
CI
level
with
the
inclusion
of
zero
point
corrections
.
.
The
large
imaginary
frequencies
associated
with
the
reactive
motion
imply
sharp
and
thin
barriers
through
which
tunneling
is
estimated
to·
be
of
considerable;importance.
Based
on
the
calculated
features
of
the
