ABSTRACT Pressure IS accepted theoretically as a useful variable However tn studtas on liquid or soltd samples It IS stlii reiatlvaiy unusual for pressure to be used as aa experimental vartable The reluctance of experrmentaltsts to use thts theoretically attractive varrable IS caused matniy by the technrcai difftcuitres assocrated with the use of sufficiently high pressures In thls talk I WIII try to show tnat m many cases the exparrmental lrmrtations are no longer those introduced by the use of high pressures Hlgh pressure spectroscoprc studies clearly imply the use of htgh pressure spectroscopic cells A brief account WIII therefore be given of the varrous types of high pressure optrcal cells which are currently betng used for spectroscopic studles Each fndivtduai high pressure spectroscopfc study has its own special justificatron However there are a few quote general observattons that can be made which cover many of the specrfic objectives of rndividuai high pressure spectroscopic studies For example frequency shifts carry unambiguous rnformahon about (I) pressure Induced anharmonic terms in the relevant potential fuficilofl Ci e the potefltlal V IS a functron of drstance d. therefore prsssure can be used to change d and study V 1 (III ail known materials undergo structural phase transitions If the form which Is thermodynamically stable under ambrent conditions IS compresssed to high enough pressuras. thase high pressure phases should be studied (III) as the application of pressure forces a material towards a phase transrtlon. the spactroscoplc study can be used to gal” tnformatron about the approaching structural instabliity. (iv) vlrtuaiiy all infrared and Raman spectra contarn examples of Fermt resonance which confuse tne lnterpretatron of the spectra and the effects of pressure are valuable alds to the correct assignment of the resonattng levels (VI pressure Induced frequency shifts can often grve extra InformatIon to help with the more reliable assignment of features within a spectrum The above points will be discussed and illustrated by examples chosen mainly from recent work by members of the spectroscopy group at King s Collage London lNTRODUCTl0.N Much of
of
producing
which
for
Thts
Is
example
fig
amblent-(effectively along
a
Ilne.
OOgP-2860/8-I/803
research
(such
produced
as at
thermodynamically
conditions (see
be
in
Interest
materials
cannot
become
the
7)
drawn Ambtent
zero)-pressure the
temperature
00
0
1981
high
diamond.
amblant
stable
usually
at
pressures
cubic
boron
pressure
under out
More
different on
a
EBerler
Sctence
nitride
are
a
dot
that
Is
Publtshers
on
-
and
B V
posstbility ate
different
phases
pressure phase
such
a
experiments scientiftcally
the
polyethylene
temperature-pressure
conditions
Much
from
generally
temperature
variable-temperature axls
comes
diagram.
diagram are
interestrng
and
located can
be
1
102 Studied
at
Interest
that
must that
region
dot. be
Is
There
waiting
also
Fermi-resonance the
work
that
oressure
has
no
an
as
are
available
The
use
of
pressure
tn
hlgh
spectroscopy
the
all
analytlcal
variable.
purooses
reflec*ts
the
ot!ier
of
that
to
work
necessarily
llmlted
by
high
thareforo
briefly
avallable thap
-__
I
more
lkbar
=
kilobar.
In
lO*Nm-2
in
of
the
high of
a
changes
about
ln
the
the
(1
variable
for
high
extra
varlable
tha
e
use
of
temperature
when
use
at
useful
research
that
are
avallable
spectroscopy
so
far
of
by
high
the
taken I
cells
required (1 8
(ii)
1
the
under
describe
ThiS
use
of
high
use
wlth
the
has
is
most
our
for
other
will
come
This
own
the
useful
paper
group
be
found
simply than
for
that
deny
that
widely
cell
the
sectlon
many
not
be IS not
now more
-
not of
consldered
purity.
etc
very the
often
sample
stability.
still
interesting
been
will
pressure
It IS
some
be
I
llmltation
results
is
Since
experlment is
temperature
will
that
high
results
apparatus
been
used
lnevltably
point
the
spectroscopic
lollawing
almost
particular
spectroscoprc all
was
Instrumental
that a
usually
that
One
spectroscopic
accuracy.
has
cell
this
__-_ IS the 1 GPa
thls
It has
that
required
range 10
mainly
reported
optical
equipment
spectroscopic
not
the Thus
IS a
London
of
rerearch
limit
the
work
been
presscre
pressure
In
performed
Col!ege
into
projects
pressure
thrOughoUt
King’s
It will
which
work
at
paper.
that
high
falls
tield
pressure
pressure IS
will
reported
research
that
from
that
spectrometer
pressure
pressure
available
h&h
factors
high
contention
pressure
the
beyond of
0
a
pressures
to
high
as
pressure
hlgh
now.
The
=
as
and
spectroscopy
forms
in
this
Olten.
kbar.
of
Idbordtories
famlllar
-___--__-_The
use
group
lhls
kbar’
aspec:s
comparable
that
active
resolution.
However.
greater
am
been
other
pressure
vlbratlon.
Informative
high
be
examples
capablllty
those
to
throughout
llmlted
spectroscopic
currently
the
limito
significance
automatlcally
I will
has
very
of
the
spectroscopy
true
has
The
part
are
the
emphaslse
equipment
been
performance
towards
be
In
pressure
supoort
pressure
the
this
1
USinQ
pressure
work
spectroscopy
that
SClentlflC
pressure-temperature
of
of
materials
had
the
the
fact
high
by
directed
L
of
of
groups
The
to have
Most work
the
trying
I have
Is of
I
high
It has
that
now
only
can
abova
spectroscopy of
for
types
avatlablllty
SpectrosCoplc
study
the
category
examples
most
most
condltlons
second
interest
that
condltlons
the
the
anolytlcal
pressure
in
Virtually
limited
to
certain
pressure
both
for
InCreaSIng
reasons
for
ambient
cover
cass
the
more
avallable
analytical
of
under
direct
aid
within
values
function
IS to The
that
of
a
intention
pressures
simple
much
However.
line
studled
du/dP
material
be
some
as
of
The
from
to
that
experlmentally
Characteristic
Spectrum
in
along
becomlng
are
variable
or
common
and
equipment
IS for phenomena
pressures which
-used
unit
in
high
pressure
research
work
103 occur
at
generally
pressures
below
accepted
for
vibratianai with
spectroscopy
pressure
smaller
than
at
rates
of
for
some
pressura
mduc_ad
frequency
defrne
qurltt
pressure.
measured
kbar
are
groups
are
and
ii
that
HIGH
the
be
most
of
be
10
the
pressure’
a
can
kodr
often
srgn
wlli
been
for
frequencies
1 kbar
the
has
defmttton
be
ten
IS close
of
most
normally
~nrt!al
rale
of
change
made
up
to
1700
shift ilmes
to
the
pressure
be
enough
of
to
frequency
with
be
of
use
of
about
in
to
thus
the
large
range
up
vIbratIona
one
or
other
relatively
to
20
those
7 Mbar) above
number
of
200
research
kbar
spectroscopy
of
short
(1
earlrer
trefs
1 and
articles
for
the
paper
EQUIPMENT
different
I will (or
tn
kbar
measurements
lncreastngly
pressure
refer
30
literature
an
pressures
high
to
However.
scale
whereas
Included
hydrostatic
been
hrgh
pressure
consfder
the
quasi-hydrostatlc)
spectroscopic
four
followlng
spectroscoprc
systems
categories systems
have
only
but
be
will
found
included Fluid
(I)
Solid
f IV) A
high
3)
Ii. 1 HIGH
Fig
and
its
pressure
generation
piston-m-cylinder
cell
spectroscopic the
scope cell
of
IS a
sample
general must
type
(DAG)
to
high-pressure
be
briefly
systems thus
htgh be
present pressure
monltored
have
been
enclosure by
constraints
also
paper with
at
least
electromagnetic
cannot
be
discussed
here
mentioned
WINDOWS
the
surrounds viewing
internal
the
enclosed
the
wlndow
P
with of
spectroscopic
window
1 shows
generatlon
outslde
the
PRESSURE
spectroscopic
wtndow
are
allow
the
pressure
anvil
pressure
Although
ref
external
untaxiai-pressure
these
to
radlation
sUppGrled
of
with
cells cells
diamond
but
A
pressure
medta
number
window
cells
media
The
descrlbsd
media
Ltquid
f II) (III)
one
day
of
SPECTROSCOPIC
the
the
but Thus
daflne
of
have
reviewed
necessary
Descripttons
to
pre&ure
‘hrgh as
Vibrattonai
spectrum
fluorescence
regular
cannot
In
pressure
1 cm-l/kbar
a
of
convement
unambiguously
unusual
recently
PRESSURE
appeared
of
magnrlude
ruby
makmg
it will
details
high
in
measurements
somewhat
I have 2)
the
deftnttron
o
on
still
order
A
dccurdtaly
(du/dP)
under
to
kbar
it IS quite
bands
requrred
Speclroscoplc as
the
shlfls
P,l
time
studied
thus
mmimum
The
this
some
area
seatmg
three In the of
most (a)
:he
nrndow the
exceeds
commonly Poulter and
window the
used window
forces ensures
contatned
types is
shown
It against that
the
pressure
of
Its
high
where support
pressure CP)
pressure
as
the The
(PSI grven
contained un-
between by
the
the
104 standard
‘unsupportsd
Fig where
the
lo
to
area’
shows
pressure
The
por Is low
l(b)
uuler
outer
PS
window
medfum
IS dropped
Ihe
the
expresston
Drtckamer
lrdnsmtttrng
p’ussure
frdcturu
support
the
PD2/(D2-d2)
(usually
OILon
along
dn
partrcularly
1s used N&I)
progresstvsiy
surfdoe
surface,
=
which
In
also lhe
hlls
wtndow
wtndow.
0~1~
soltd
If non -amblont
msdla
the
narrow
ports
say
Ol
cells window
until
I: is
too
Is
used
sapphtre
tomperaturos
are
to
be
used Fig gasket
l(c)
so
Thts
fluid other
shows to
as Is
types
tne
generate
shown
of
cell
rn
opposed
force
a
higher
pressure
DAC
configuration.
the
window. in
where the
the
gasket
but
window
than
it has
Is
in
been
iorced
the
used
onto
a
enclosed successfully
In
also.
ta) Flg
1
Three forms of high pressure spectroscoptc windows (a) Poulter. (bl Drtckamer Cc) Opposed force (DAC) marked W the axts of the lrght path IS marked L. and pressure P Four
strength
types
may
of
limit
experimental the
maxtmum
may
ltmtt
the
spectroscopm
may
limit
the
radlatlon
become
unusuably
scramble
Constderatlons spectroscopic has
posstble
refs us
I
to
found
S.
burst
t
IS the
are
For
(ref at
should
4)
glass given
thickness
can
be may
that
the
It
a
D
IS
of
by the
may
P
=
diameler
(1)
Its
ratio
be
Ita
absorptton (1111
such
compromlse
a
standpoint apprecrated
corractly
size
may
as
to
glass 64
(t/D1 01 the
and a
between large the
how
shaped
wtndow-burstrng float
Its
signal-to-noise
tnevitable
over
from
approximately and
(II)
collected
IS
radiatlon
generally
set
cut
be
window
Spectroscopically
mounted
recent
wmdows
the
the
the
attained
high-pressure
not
IS
properly in
a
by
propertres
by
requirements from
Imposed
data
point
represent
used
are
example. that
pressures
wtndcw
(III)
be
the
carrleo
whereas
they
which
11s blrefrrngence
high-pressure
when
6)
and
advantage;
window
materials
( iv)
Information
(i)
and
stQntficart
to
be
that
ovar
throughput
small.
may
pressure
range
polarlzatio-t
ihe
lrmttatlon
The wlndow the rstatnsd
tests
strong
where
wrndow
supports. up
prsssurrzsd
unsupported
window smallsst
P
to
(see 20
kbar.
wlth
Octoll
IS in
kbar.
area
That
105 expresston
should
windows
have
45
(ref
kbar The
to
ail
is
to
significant
not
laser
beam
radiatron
can
collected
through
3
II
HIGH
2
A
and
wade
four
gas
compressor
Clearly
cell
IS
Itself
requires Cells
the with
too
identical
many
have
of
the
windows
but
up
to
glass
at
least
I
other
support
gases
of
and
that
can
be
applred
the up
liquids)
agaln
in
about
be
taken we
thts
way
20
than
simple
mlxlng
of
In
refs
I and
traced
in
indrcate
kbar
has
a
srgnal
the
some
3
the
d&all.
with
many
literature
slngie
IS
by
to
be
piped
over
example
any
from
sets
the
from
‘fluid
such
at
an of
77
K
external
the
a
maraglng
specific
ceil steel)
The but
It
experimental
cell
conflict
too
between
Commercially present
the
system
tne
requirements kbar
of
primarily
one
into
from
weaken
posslbie
lt
removing
made
for
ceil used
into
generatlng
made
a
window been
pumped
could (It
not see
two
it
pressure
could be
be
mounted
construct
hrgh-pressure to
more
IO
are
exte:nal
must
Here
wlndows
used
an
m
can
type
about
(or to
Raman
7)
descrrbed
a
srze
to
geometries care
no
samples
simple
convergmg without
dlverg,ng
effects
of
less
surfaces
slowly
window
a
these
are
window a
are
edge
earlier
actual
Solid
the
pressurrzed
studied
that
generatlon’ up
They
Thus
conslderable
rref
are
do
lrsted
half
relatively
ba
have
they the
CELLS
cells
can
a
clear
lsotroprc
once
wmdow
Whereas
suffer
Whaiiey
development
pressures
can
and
different
pressure
that
can
We
lkawa
the
angle
of
even
near
through
other
centre
because variatrons
pronounced of
~111 be
strain-Induced
Is
more
middle
some
SPECTRCSCOPIC
about
but
spectroscopic
tested
index
scramblrng
wlndow
catagorles
different
requirements
kbara.
and
ana/or
perpendicularly
the
system
windows
passes
the
through
of
axternal
heitum
20
5)
This
much
In
components
at
shows
are
porartzatron
Here
the
are
passed
hrstorrcal
of
they
range natural
refractive
at
the
years
medium
of
llmlt
tref
self-evident
through
an
range
to 30
2
be
as
past
each
wllh
4)
so
which
PRESSURE
references
kbar
the
passes
slgniflcant
poiarlzed
rrefs
experlmental
25
transmission r Iv)
effects
than
which
any
dlffarentiy
to
strain-induced The
area
light
the
(II)
necessarily
pressure
suffering
Fig
of
develop
for
for
our
up
However
unsupported
than
beyond used
6)
materrais
subjected
used
been
significance
brrefrrngence
the
be
spectroscopists
wrndow
the
not
certainly
upper
much
by
available limit
rnciudlng
the
to
the
tubing pressure
106
Fig
2 a
Tno-wmdow
high
pressure
opbcal
cell
0b
Frg.
2(o)
Cell
mounted
vltnin
cooling
jacket
107 A hlgh
pressure
Raman
HIGH
hand
pressure
p&ton
It friction double (A2/AT)
of cell
quoted
Into the
range
used
up to perhaps
short
fatigue
of
the higher
set by the hlgh-pressure piston.
pressures
piston
up to perhaps
4)
Thts
IS required
drives
the
to supply
small
area
within
which
the sample
to rest
when
the
I e
when
grves
the
for
or
ultimately Wlth
the
careful
50 kbar
long
windows
should
= P2A2
pressure
IImitation
multiple
a fairly
The
PTA1
of
working
could
design.
Pt
lrmrtatlon
the = Here
on
cylrnder
life.
or
IS
higher
if a
carblde
the 45
be
to
probably
a tungsten
this
could
smaller.
lrmlt woulo
usrng
be possible
on
or
15 or 20 kbar
be made
pressure
IS mounted
factor
component
a
hlgh-
net force
lntenslfmation
The
a pressure
be tolerated and
WITH
comes
autofrettaged
pressures
(ref
IS possible
Usually
twice that figure
In fig 3
cylinder zero
geometries
USE
assembly
ram
of the areas
a properly
life could
gauge
area
piston
obvtous
FOR
type cell
pressure
becomes
the ratio
IS less
However
withstand
the
IS shown
tbar
liquid-filled
then
Thus
again _ a wide type
and
type
CELL
lntensifler
arrangement
Pp
I4
to the large
is Ignored
piston
TO
3
pump
low pressure
intenstfler
RAMAN
MEDIA
Fig A small
of the
PRESSURE
LIQUID
known
cell
kbar
be
106 window
testing
Fig used
system
4 shows
by cur
Infrared
transmission 77
tusualiy
NaGI)
K and
into the cylinder
jacket
which
lntenslfier
difference
hydrostatic medium
the central
the
part
the use peak
of the cell
but with a short
hbar.
(50
transmrtting
seen
kbar)
steel
life of perhaps
halide
carbide
piston
its outer-
cell
which 9)
whrch
pressure
The
a non-
solid
avolds
matsrrai
the
Note
operates
cycles.
an
The
applies
which
wrndow
cyirnder
20
alkail
to contain
to a br:ttle
for
to be essentially
tref
that
up to 50
after
whrch
It IS
replaced A diamond shaped. surface IS a
anvtl cell
bounded of the
!iuId
However a sample.
tor
for
small
hale
that
*soft scircl’)
a
hard
which
(DAC)
by the hrgh
solids
(or
IS smaller
IS shown
pressure
end
IS drilled
I”
it can when than
@
occupy
frg 5
in
the
cwntrw
the whole
hydrostattclty the
sample
of
the
high
4
Drickamer
with a fluid
medium
cell
fief
6).
IS drsc inside
If the
sample
volume
pressure
CARBIDE
type solid
the
it IS usual
ALL OTHER PART9 KE 6% STEEL Fig
volume and
gasket
pressure
IS importart)
hole.
gasket
NNCSTEF!
The
fiats of the dramonds
1
been
at temperatures
an
within
medium.
caster
has
primarily
the tungsten
mounted
type windows
IS a supported
working
Is
way i3 that of the fig.3
but IS much
of Drickamer
pressures
When
it IS clearly
m a simriar
to the sample.
allows
to bpply
ram
medium
of this type
which
up to 50 kbar
by forcing
halide.
1s the soled pressure
pressure
also
a low pressure operating
range
cell
cell
it Is intended
transmitting
Is generated
with alkali
type
years
pressure
pressure
pr-sssure
a one-window
of a Drrckamer
10’ many
in the The
filled
contains
type cell.
prmcipai
need
K
Is effectively
part
(ref.81
spectra the
which
6)
pressure
group
600
and
ref
hlgh
research
between down
of
the
to surround transmitter
109
Fig The
Inevitable
requirement that
must
end
fiats
of
The of
the
that
in
no th3
end
successfully large
In
of
high
present A
day
VIS
UV
conductlvlty scatterlng the of the
transitions
X-ray
diffraction
e xperiments the
experiments
extrameiy
small
could
performed volume
Clearly
the this
and
exampls
high
end
work
up
to
70
work
up
to
400
kbar.
IS less
aperture smaller
than
fiats
pressure
for
much
1s very
small
(usually
studies Many
spectroscopic
pressure
for
window is
the
high
but
kbar than
the
half
apertures
windows
volume
space
used
10)
other and
types
DAC
certainly
s
the
the
with of
DAC
IS be:ng
interferometers) experiment
are
probably
most
widely
and
are
quite
also
We
most
used
type
popular of
system
research a
commercfally
heatlng
avallable
melting.
reactlon
growing ba
wlthin that
Mossbauer klnetlcs.
ruby
performed DAC’s
IS available
DAC
fluorescence.
compresslbllity
crystal
that
recommended
spectroscopic
for
VlSCOSlty
solublllty
For
tref and
smaller
required
typlcaiiy
ceil
Plermarlni design
the
are
studies
phase
of
are
sample
advertisement
cryogemc
are
lnrrared
pressure
terms
mm
sample
optical
high
recent
tiny
and
high-pressure
in
IS effectively
for
some
Block
mm
dlametQr
Raman
that
pressure
ObseNatlon NIR
of
4
which
used
for
wlthln
0
avaliabie
used
number
performed type
the
the
DAC
1 2
than
flat
conventionally
a
after
pressures
about
gasket
diamond
are
ior
If higher
more
ceil.
between
seen
diameter
Although
a
be
used
of
hole
anvli
compromlse can
Se
d&meters
Diamond
5
in
the
have
and
under
NMR
been
truly
high
Brlllouin as
some
within
in such
of Some
pressure
remarkable
working
Raman.
electrical
measurements’
cell
However
I R effect
dlfiuslon
pressure
‘visual
i&ted
v’ew a
of small
volume
doss
pose
procedure the
two
fiats
another wifh
high
must
up
a
cell
this
does
sourcQs.
require quite
capable
Ill
are
not
The
the
dnd
small
The
Informdtlun
oven
with
pressure
levals
that
intensity changing
the
by
the
The
(le
2)
d
a
laterally
remarn
parallel
to
a
design
the the
most
hrghQ*#t
anvils
delay to
in
In
3
rn
the
available
or
to
form
of
4
r They
do
(by
not
the
yet
relahvely
Unfortunately that
It
broken
they
use
way
high
from
However be
srnce
rodtme
figs
even
pressures
not
dellvery
rmagfne
those
popular
versatrle
are
but
prOCQdUr9
avaliabie
stahc
surprrsrngiy
up
and
one
problem
settlng
commercially
the
trrvlai
such
DAC
s
are
-measured shapes
a
here
‘normal’ v2
to
Lntensltles
consrder
band
might
dnd
spectroscoprcaily
and
be
changes
in
of
these
Y
but
the
7 and
gives
may
of
bands
wlthln
‘expected’ 2)
prove
to
abnormal
rt can
linearly
very
a
variattons
However
roughly
only
well
funchon
Y approxrmdtely
ChdngtQ
it IS the
a
various
change
this
should
changes
band.
to
the
detail
refs
eXpQCted
~ntensilies
‘normal’
In
(See
as
of
with hnear
slowly
wrth
with
contarn
useful
behavrour
that
Is
rnterestmg most
hydrogen
frequencies
---
intensihes
are
insensihve
but a
slowly
X-H
witn
pressure
dt
rise
bonded
resonating
sometimes
a
oressure.
show
bands
spectrum
as
approximately
frequencres
to
can Most
a
pressure
(and
stretching
one-another
rs changed
glvsn
literature
now as
a
It was
possible
monatomlc
soilds.
examples only
is
a
allgned
durrng
DAC
nut
will
structural
but
very
shift
cr
two
raptd
slowly
change
Ilnearly)
usually
involving In
relative
continuously
abruptly
chemical
bands
changes and
with
decrease
with
and
change
is
induced
pressure
spQctroscoplcally and
for
pressure.
discontinuously
be
as
percentage
Most
are
as
to
easier
such
are
magrutudtls
more
but
the
Is
is
carefully
and
this
diamond
may
space
sh._fpus
example.
pressure.
if the
commercially
general
bdnd
prsssure
For
of
ingenurty.
It is
cells
for
(for
scientifically
1
IS not
in
:he
up
which
that
pressure.
that
up
littie
there
another
required
DAC
very
self-contarned.
working a
frequencies.
p’rameters
shown
fact
the
be
STUDIES
There
these
PI
of
parameters are
spectrum.
be
and
present
EXPERIMENTAL
pressure
of
at
of
Items’
operators)
one
is
up
must
Scme
care
the
setting
‘stock
to
small.
with
expensive.
unskliled
great
settrng
flats
pressures
alter
and,
and
Qnd
parallel
it Is
careful
be
to
cells
not
equipment
several
seem
made
wall-deslgnad
currantlyavaiiable
are
be
highest
All
to
problems
pressure
the
pressure
doQS
special
The
from
most
contains function to AS
examples of
systematically type
categories
of
pressure
crystals. Here
most In
the
consider
is
of
longer
the
dlatcmlc there
types
material review
different
molecular
space
for
studied articles
types
of
crystals one
or
two
(rafs
I
materlal. 1 givlflg key
examples
111
b
’
0
I
2
3
4
5
PRESSURE/K
Fig
6
Frequency
Fig
6
In
the
far
I”
regions
shows
like
can
quite
precisely
type
be
0r
In
this
A
the
of
molecule
the
VII+VIII
which
slrongly
flrsl
VIII
looklny
curve exlend
examples show
that
0
pressure
(refs
of
as
mode
lncludad
energy are
RhBr
to
is
good
to
change
phdse
11
(I)
high
define
(NaCI
even
pressure
Cdu/dP),
II-I frequency
lrdnsltion
12)
measured
emphaslse
low.
enough
dlscontlnuous
lanes
to
about tho
15) 190
phase
2.04*
beyond
be
looklng fig
kbdr
trtple
at
the
phase
wlthln
Into point
of
In
10
type
that to
to
1s
CsCl
vlctnlty study
the
tceVl
region
for
pressure VI+VII
III*IX
ax!s
which
and
show
the
but be
recent
that
mentioned
of
ice
VII
161
have
et
that
al
(ref
VI-VI the
triple
approached
curve from
which Klug
and
ice
been
point.
Ilquld-Ice
IceVl-hqurd
work
stud!es
be
liqutd
the
other
01 the
of
should
Plermdrlnl
showed
spectra
aspocls
spectrum
H20
Infrared
then
the
Raman
two
Figures
of
latter
the
axis the
and
In IS
transltlons.
V-VI.
various
Ihe
diagram dtagram
order-dl=order parallel
diagram
could
phase
studying
This.
which
phase
This
Illuslrdle
three
DAC.
the
complex
1~111. Ill+V
studying a
(a)
been
and
those
been
GPa)
extendsd the
7
hdve
diagram
02
9.9
7
temperature
14)
13
a
fig
virtually
10 the
figures
before
(ref
could
dnd
It shows
c,langes.
(refs
forms
has see
transmon
recently
at
T
kbar
order
slructural
hdvo ILL
(69*2OC.
ftrsl
IS H20.
parallel
lo
5
never-the-less
kbar
virtually
Whalley up
strongly
25
order
slgnlllcance
dnd
or
of
been
available
4
function
the
has
(1113 the
bands
lines
Howover have
the
even
as
on
This
where
that
below
(b)
Wo
RbBr
pressurs
12)
(II)
d
of
7
case)
and
dlrforont
of
and
out many
for
lrdnsitlon
mode
I R
for
range
lnlerestlng
far
errec:
small
pressure
0
effect
11
carried
iho
T
the
(refs
I R
work
typlLdI
of
6
BnR
that
VII
melting
would
not
dlrectlon
ll.2
Fig
7
Phase
diagram
of
Ice
I 0.oall 148 K cm-1
GPa
4
0.27 -a 165 K 3 cm-1
o-29
246 K 3 cn-1
0.28 150 3.5
GPa
CPa K ca-1
0.44 Gla 148 K 4 an-1
I
1
333x>3loo
0
ivcD.f-’ Fig
8
Raman
speclra
of
ices
I. II. III. IX.V.VI
and
VW
113 Fig
9
shows
I. II. 111 IX. V VI between for the a
the
the ice
tranlahonat
13)
spectra
various has
very
the
Cref
for
and
way
promrnent
phase O-H
of
diagram
mode whereas the
the
transtttons the
Thts
At
O-H--
0
mode
longer
O-H--
frequencies
Flg
9
of
distances Increases 0 In
Ice
In
any
but
Frequencies lunchon of
terms.
In
long one
9
tref
a
shown
O-H stretch and pressure passtng
ICE,
spsctra
whtch
Raman
0 O-H
the the that
wrth
Within
phase
varrous
the
stretchmg
pressure
effecrts
the
scan by
of
relationshtp dlsttncttve
that
vary
13)
denser
O-H--
It IS clear
O-H
tncreasrng
phase
relatively as
the
These
bonds
favours
that
fig
top
spectra
unambrguously polnt
frequencras
with In
Raman
completely
show
general
the
order-drsordsr
phase
spectra
offer
dtagrams
way
decreases
distances these
the
mode In
transItton
hydrogen
that
the
latttce
of
the
otherwtse
phase
decreases
a
th-
spsctra
tllustrates out
region
Ncrtce
and
tllustrated
IS
mode
17)
Raman
compare
mode
the
show
lattme
to
lattme
strengths
thts
frequency
Increases
III
mapprng
translatronal
stretching
trnf
These
adopted
reltable
latttce
VIII
IX and
phases
It IS intereshng most
and
be
distances frequency
promrnent through
I must
increases
In
terms
reduces
decreases soas
reverse be
the
phase
pressure
and to
In
to
be
translatronal lattrce vartous phases
the
produce
steps
expected
the thts
lattice
stretch
The
changes
disconttnuous
phase the
drscussed
As
and
across
one
O-H
structures
structure
Ice
any
whereas
the
can
frequency pressure
mode
the a
IS a
of
114 relatively
unstable
G-H---
short support
0
hlgh
structure
with
pressures
respect
Even
dletancee. as
at
shown
by
our
to
nottce
the Thts Ice
10
spectra
shows
an
are(l)
transthon second
just
We systems small
Ice
I-IX
The rrght
hdd
a
Infrared of
bands
lempernture)
dre
very
usually
unamb
quote
stable
at
because polnhng phase
long-term and whrch
guous
mleresl
Aamdn at As
cusp
I”
the
speclrd
of
low the
S.peCl’d
the
to
these
drH
The
two
IS no
pornh
and be I.
seems
(II) I-II Ice
III
to
temperatures
alkalr
halrde/rmpurrty
contarn
somohmos cledr.
main
me
dragram
lowest
systems
IX
It should
there
of
(and MI
I and
temperature
phase
tho
speclra
tomporatures
low
ices
suggests that
In
dragram
of
at
dragram
tt suggests
dawn
18)
b&
K study
88
pressures
phdse
the
not
3
pressures
recent
high
of
will
km-‘)
various
this
the
the
Cref
1
Shift
downward
sharp
K studles.
250
K and
although
because
strucxture
D20
from
IS rnloreshng
pomtl
The number
88
Example
open.
have
at
I IS not
1s from pornt
II trrple
rematn
88
150
Raman
pressure thls
I
Reman
Ftg
recent
I
50
10
increasing
temperattres
bar
1 1
Fig
to
low
the
a oven
Ion
relatrvely at
rnturpretat!on
room is
115
Fig
Pressure-scanned The at 80 K. for the sample are indicated
11
Fig for
11
shows
5 dlfforenl
which
spectrum shown bwcond
lo
horo. by
the
Virtually are I
ono
ali
to
Rdmdn
dfld
Idttlce
two
hrgh
-
of
aro
variable
pressures
could
amblent
condltlon
spectra
qu110 expose
find
KBr/CaSOq
dre
The Iwo
rut-don
d
scanned
two
points
strong
Fermi-resonance
contain the
all
bands
redson
of
MI the
for
pressure
this
(II)
IS the
oxamplos
‘lattice
modes)
lniernal
mudu:. to
of
Fermt-resonance
assignments
contain
expected
side
which dre
band’
are
close
drdmdtlcaily
to
features
usually
too
weak
one-another
enhanvce
the
ln
to such
lntenslty
of
symmetry
general theso
many
of
19)
lhere
ds
exiernal
dpproprlate
tref
feature
speLtrd
sollds
be
tho
upsetting
dnd
can
to
band
Rdmdn
whurw
of
points
prossuros
slds
Internal
bdnds
dnd
spectrum
4bar
(1)
changes
thoreby
spectra of
rwondnce
side
Thbise of
dnd
Iiowover
Form1
soma
lnlenslty
the
7 3
dre
!b oxpociod
Ignored
of
1 and
study
Idtticw
Infrdred
confuslon
spectra
a
region
5
thl:.
reldtlve
comblnaitons
~dubt)
use
whore
usually
R
(brndry
dboul
IS due
wide
cm-l between
make
rdpld
bdnd
which
20
pressures
wish
I
a
Fermi resonance In the Infrared spectrum of KSr/CaSO4 narrow spectral range (1070 to 1090 cm-l) was recorded subjected to the five different pressures of hehum gas that
although elrects
roullne
lhey
dre
usually
IS the
basis
of
appllcahons
in
the
the
ignored
The
contentton
that
Inlerpretatlon
of
CONCWSIONS used
I high
much
pressure.
relatively
and
little
space
However characteristic lattice sufficient
side
of
the how for
I hope
reason
one
I
for
have
induced
features a
more
space
might
showing
that
pressure band
available
set
about
examples shown frequency
which
explaining
are
routine
of
use
doing what
enough
to
shifts.
relevant of
why
to
(ii)
so has
might
This already
support
the
left
wish
Idee
as
all an
to
me
been
work
at
with
done that
Fermi-resonance
virtually
pressure
one
spectra. experimental
(I)
and
(1111
constttute variable
a in
116
spectrnTcoplc Secondly research. pressure future
studies I hope that I have conveyed
where phase
the
Investigation
dlagrams
gsieratlons
must
some
of the ever
hold
many.
of the excrtement
expandlng
regfions
as yet unexpected.
of high
pressure
cf temperaturesurprises
In store
for
of scientists
ACKNOWLEDGEMENTS
1 gratefully acknowledge the flnanczal support gl\en by SERC, the Paul In;trumont facllnies
1. 2 3 4 5 H 7 8 Y 10
11
I.?
13 14 I’) lb 17 lb 19
W F
Fund at King’s
and
the
U S
Army
In setting
up the
high
pressure
spectrocoscoprc
College
Sherman and G R Wilkinson. Chapter 4 pp 158 to 336 vol 6. ‘Advances In Infrared and Raman Spectra’ CEds RJH Clark and RE Hester) Heyden. London C1980) _ W F Sherman. Bulletin de la Soclete Chlmique de France No 9-10. 1347 to 1369 C1982) W F Sherman and A A Stadtmuller. ‘Experimental Techntques in High Pressure Research’ to be publlshed by Wiley (1984) King’s College London (1982) A 4 Stadtmullar. PhD Thesis E Whalley. A Lavergne and P T T Wong. Rev Sci lnst . 47.845 (1976) Itav Scl lnst 52.962 C 19791 F Whalloy and A I avorgno. S lkawa and E Whatley. IX AIRAPT conference. Albany Cl9831 W F Sherman. J Scl lnst s-462. (1966) HA I--Ilch. r E Slykhouse and H G Dr1ckamer.J Opt See Am 47.1015 (1957). S Block and G Plermarml. Physics Today. 44 CSept 1976). R P Lowndes and A Aastogi. Phys Rev m-3598 (19781. M S Shdwyur dnd 31 F Shurmdn. Infrdrad Physics 18.909 C 1918) and 22. 23. C19821 King’s College London C1982) B Sukarova. PhD Thesis. B Sukarova. J Mel Srr 80.217 C 19821 W F Sherman and G R Wilklnson I> I) Kiu9 drld I Wtlcilluy IX AII(AI’I ~onluroncc. Albany C IYtlJl C_, J I’rorrndrrnr. It L Muriro dnd t Mock. IX AIItAI’T uunforoncc. Albany C lY83) P T T Wong and E Whalley J Chem Phys 64.2359 Cl9761 G I- Slark. A K Gdr9. W I- Strormdn and G ft Wilkinson. tUtihlOS XVI C 1983) S I CWIL dnd W I- Shormdn. Spoulrochlm Acta. 3a b fJ C 1979)