<s>
PQS	B-Language
is	O
a	O
general	O
purpose	O
quantum	O
chemistry	O
program	O
.	O
</s>
<s>
Its	O
roots	O
go	O
back	O
to	O
the	O
first	O
ab	O
initio	O
gradient	O
program	O
developed	O
in	O
Professor	O
Peter	O
Pulay	O
's	O
group	O
but	O
now	O
it	O
is	O
developed	O
and	O
distributed	O
commercially	O
by	O
Parallel	B-Language
Quantum	I-Language
Solutions	I-Language
.	O
</s>
<s>
The	O
origin	O
of	O
PQS	B-Language
program	O
was	O
developed	O
by	O
Meyer	O
and	O
Pulay	O
in	O
the	O
late	O
1960s	O
.	O
</s>
<s>
Then	O
,	O
Meyer	O
named	O
it	O
“	O
MOLPRO	B-Application
”	O
and	O
used	O
Gaussian	B-Application
lobe	O
basis	O
sets	O
.	O
</s>
<s>
In	O
the	O
1970s	O
,	O
the	O
current	O
version	O
of	O
MOLPRO	B-Application
added	O
a	O
number	O
of	O
advanced	O
methods	O
such	O
as	O
multiconfiguration	O
self-consistent	O
field	O
(	O
MC-SCF	O
)	O
and	O
internally	O
contracted	O
multireference	O
configuration	O
interaction	O
(	O
MR-CI	O
)	O
.	O
</s>
<s>
Simultaneously	O
,	O
in	O
the	O
1980s	O
,	O
MOLPRO	B-Application
was	O
extended	O
and	O
mostly	O
rewritten	O
by	O
Hans-Joachim	O
Werner	O
,	O
Peter	O
Knowles	O
and	O
Meyer	O
's	O
coworkers	O
.	O
</s>
<s>
They	O
wrote	O
a	O
new	O
program	O
called	O
TEXAS	O
based	O
on	O
the	O
original	O
MOLPRO	B-Application
and	O
replaced	O
Gaussian	B-Application
lobe	O
functions	O
with	O
the	O
standard	O
Gaussian	B-Application
functions	O
.	O
</s>
<s>
In	O
1996	O
,	O
Baker	O
joined	O
Pulay	O
and	O
,	O
around	O
the	O
same	O
time	O
,	O
Intel	O
brought	O
out	O
the	O
Pentium	B-Device
Pro	I-Device
,	O
a	O
processor	O
for	O
PC	O
that	O
was	O
competitive	O
with	O
low-end	O
workstations	O
and	O
less	O
costly	O
by	O
around	O
an	O
order	O
of	O
magnitude	O
.	O
</s>
<s>
Understanding	O
the	O
capability	O
of	O
this	O
improvement	O
for	O
computational	O
chemistry	O
,	O
PQS	B-Language
was	O
formed	O
and	O
a	O
SBIR	O
grant	O
application	O
was	O
submitted	O
in	O
July	O
1997	O
for	O
the	O
commercial	O
development	O
of	O
PC	O
clusters	O
for	O
parallel	O
ab	O
initio	O
calculations	O
.	O
</s>
<s>
In	O
the	O
meantime	O
,	O
the	O
Pulay	O
group	O
,	O
financed	O
by	O
a	O
National	O
Science	O
Foundation	O
grant	O
,	O
set	O
about	O
constructing	O
a	O
Linux	B-Application
cluster	O
using	O
300MHz	O
Pentium	O
II	O
processors	O
.	O
</s>
<s>
The	O
PQS	B-Language
programming	O
was	O
demonstrated	O
on	O
the	O
TEXAS	O
code	O
and	O
parts	O
of	O
it	O
,	O
chiefly	O
the	O
NMR	O
code	O
,	O
were	O
authorized	O
to	O
PQS	B-Language
from	O
the	O
University	O
of	O
Arkansas	O
.	O
</s>
<s>
The	O
basis	O
capabilities	O
in	O
high-level	O
correlated	O
energies	O
for	O
PQS	B-Language
ab	O
initio	O
v	O
.	O
4.0	O
include	O
MP3	O
,	O
MP4	O
,	O
CID	O
,	O
CISD	O
,	O
CEPA-0	O
,	O
CEPA-2	O
,	O
QCISD	O
,	O
QCISD(T )	O
,	O
CCD	O
,	O
CCSD	O
and	O
CCSD(T )	O
wavefunctions	O
;	O
enforced	O
geometry	O
optimization	O
(	O
used	O
,	O
among	O
other	O
things	O
,	O
to	O
simulate	O
the	O
results	O
of	O
Atomic	O
Force	O
Microscopy	O
(	O
AFM	O
)	O
experiments	O
)	O
;	O
full-accuracy	O
,	O
canonical	O
UMP2	O
energies	O
and	O
analytical	O
polarizabilities	O
and	O
hyperpolarizabilities	O
for	O
HF	O
and	O
DFT	O
wavefunctions	O
.	O
</s>
<s>
An	O
efficient	O
vectorized	O
Gaussian	B-Application
integral	O
package	O
allowing	O
high	O
angular	O
momentum	O
basis	O
functions	O
and	O
general	O
contractions	O
.	O
</s>
