<s>
In	O
physics	O
,	O
the	O
elastic	O
potential	O
energy	O
gained	O
by	O
a	O
wire	O
during	O
elongation	O
with	O
a	O
tensile	O
(	O
stretching	O
)	O
or	O
compressive	O
(	O
contractile	O
)	O
force	O
is	O
called	O
strain	B-Algorithm
energy	I-Algorithm
.	O
</s>
<s>
For	O
linearly	O
elastic	O
materials	O
,	O
strain	B-Algorithm
energy	I-Algorithm
is	O
:	O
</s>
<s>
In	O
a	O
molecule	O
,	O
strain	B-Algorithm
energy	I-Algorithm
is	O
released	O
when	O
the	O
constituent	O
atoms	O
are	O
allowed	O
to	O
rearrange	O
themselves	O
in	O
a	O
chemical	O
reaction	O
.	O
</s>
<s>
The	O
external	O
work	O
done	O
on	O
an	O
elastic	O
member	O
in	O
causing	O
it	O
to	O
distort	O
from	O
its	O
unstressed	O
state	O
is	O
transformed	O
into	O
strain	B-Algorithm
energy	I-Algorithm
which	O
is	O
a	O
form	O
of	O
potential	O
energy	O
.	O
</s>
<s>
The	O
strain	B-Algorithm
energy	I-Algorithm
in	O
the	O
form	O
of	O
elastic	O
deformation	O
is	O
mostly	O
recoverable	O
in	O
the	O
form	O
of	O
mechanical	O
work	O
.	O
</s>
<s>
Compounds	O
with	O
unusually	O
large	O
strain	B-Algorithm
energy	I-Algorithm
include	O
tetrahedranes	O
,	O
propellanes	O
,	O
cubane-type	O
clusters	O
,	O
fenestranes	O
and	O
cyclophanes	O
.	O
</s>
