<s>
In	O
molecular	O
mechanics	O
,	O
VALBOND	B-Algorithm
is	O
a	O
method	O
for	O
computing	O
the	O
angle	O
bending	O
energy	O
that	O
is	O
based	O
on	O
valence	O
bond	O
theory	O
.	O
</s>
<s>
The	O
VALBOND	B-Algorithm
functions	O
are	O
suitable	O
for	O
describing	O
the	O
energy	O
of	O
bond	O
angle	O
distortion	O
not	O
only	O
around	O
the	O
equilibrium	O
angles	O
,	O
but	O
also	O
at	O
very	O
large	O
distortions	O
.	O
</s>
<s>
This	O
represents	O
an	O
advantage	O
over	O
the	O
simpler	O
harmonic	O
oscillator	O
approximation	O
used	O
by	O
many	O
force	O
fields	O
,	O
and	O
allows	O
the	O
VALBOND	B-Algorithm
method	O
to	O
handle	O
hypervalent	O
molecules	O
and	O
transition	O
metal	O
complexes	O
.	O
</s>
<s>
The	O
VALBOND	B-Algorithm
energy	O
term	O
has	O
been	O
combined	O
with	O
force	O
fields	O
such	O
as	O
CHARMM	B-Application
and	O
UFF	O
to	O
provide	O
a	O
complete	O
functional	O
form	O
that	O
includes	O
also	O
bond	O
stretching	O
,	O
torsions	O
,	O
and	O
non-bonded	O
interactions	O
.	O
</s>
<s>
For	O
hypervalent	O
molecules	O
,	O
the	O
energy	O
is	O
represented	O
as	O
a	O
combination	O
of	O
VALBOND	B-Algorithm
configurations	O
,	O
which	O
are	O
akin	O
to	O
resonance	O
structures	O
that	O
place	O
three-center	O
four-electron	O
bonds	O
(	O
3c4e	O
)	O
in	O
different	O
ways	O
.	O
</s>
<s>
More	O
recent	O
extensions	O
,	O
available	O
in	O
the	O
CHARMM	B-Application
suite	O
of	O
codes	O
,	O
include	O
the	O
trans-influence	O
(	O
or	O
trans	O
effect	O
)	O
within	O
VALBOND-TRANS	O
and	O
the	O
possibility	O
to	O
run	O
reactive	O
molecular	O
dynamics	O
with	O
"	O
Multi-state	O
VALBOND	B-Algorithm
"	O
.	O
</s>
