Analisi fine della materia disordinata• Personale CNR:

– Marco Zoppi primo ricercatore– Ubaldo Bafile ricercatore– Lorenzo Ulivi ricercatore– Milva Celli ricercatore– Daniele Colognesi ricercatore

• Collaboratori– Francesco Grazzi Assegno di ricerca– Alessandra Giannasi Dott. Ricerca– Giacomo Corradi Borsa di studio CNR

Descrizione del gruppo• Base culturale comune: Fisica dei Liquidi

– Struttura microscopica - potenziali intermolecolari– Dinamica microscopica - proprietà di trasporto

• Caratterizzazione: sperimentale– Spettroscopia ottica

• Scattering Raman (livelli inter- e intra-molecolari)• Scattering di Brillouin (modi idrodinamici)

– Spettroscopia e diffrazione, neutronica e X– Simulazione (MC, MD, PIMC)– Fisica delle Alte e Altissime Pressioni

• Impegni (tempi brevi):– strumentazione avanzata per neutroni– immagazzinamento di Idrogeno

microscopic structure and dynamics of fluids

positions motions

potentials

simulation

pressure

density analysis

diluted gasesliquids

microscopic structure (and dynamics) of fluids

molecular crystals

ultra-high pressure(Mbar)

multi-componentsystems

neutronsX-rays

structural transitions

diffraction

D.A.C.

NIMROD

positions motions

simulation

potentials

density analysis

diluted gasesliquids

pressure

INES

microscopic (structure and) dynamics of fluids

D.A.C.

collectiveself

neutron scattering

I.R.absorption

motionspositions

simulation

potentials

density analysis

diluted gasesliquids

pressure

incoherent coherent

light scattering

X-ray scattering

TOSCA Density of States

multi-componentsystems

a neutron scattering experimentincident neutron 00 , kE

rh

scattered neutron 11 , kE

rh

energy transfer 10 EEE −=

momentum transfer 10 kkk −=

)cos(2 102

120

210

2 θ−+=−= kkkkkkk

neutron diffraction (k0 = k1)

)cos1(2 20

2 θ−= kk

[ ]π

σ+−

πσ

=⎥⎦⎤

⎢⎣⎡Ωσ

41)(

4totcoh kS

dd

]1)([1)( −+= ⋅∫ rgednkS i rkr

-4 -3 -2-1

01

23

4 -4-3

-2-1

01

23

4-3

-2

-1

0

1

2

3

4

( )∑ −⋅−=lj

i jleN

kS,

1)( RRk

Problem: the structure liquid Hydrogen• the most abundant element in the universe• the simplest atomic system• the simplest molecule

• no structural information until 1989: why ?

• molecular hydrogen carries 2 electrons only• practically invisible to X-rays

• neutrons?

hydrogen and the neutronsneutron cross section: inccohscatt σ+σ=σ

barn76.1=σcohproton coherent cross section:

barn91.79=σincproton incoherent cross section:

much better situation for deuterium

barn60.5=σcohdeuton coherent cross section:

barn03.2=σincdeuton incoherent cross section:

quantum Boltzmann liquids: structure of deuterium

0 5 10 150

1

2

3

4

Experiment Intramolecular cont.

dσ/dΩ

(bar

n/m

olec

ule)

Q(A-1)

0 1 2 3 4 5 6 70.0

0.5

1.0

1.5

2.0

2.5

EXP. PIMC NWB PIMC LJ

S(Q

)

Q(A-1)

M. Zoppi, U. Bafile, et al.:P.R.B 48, 1000 (1993)P.R.L. 75, 1779 (1995)P.R.E 54, 2773 (1996)

Exp.:SANDALS @ ISIS

liquid hydrogen structure

0 1 2 3 4 5-1.0

-0.5

0.0

0.5

1.0

1.5

S(k)

-1

k(Å-1)

0 2 4 6 8 10 12 14 16 180

1000

2000

3000

4000

5000

6000

Cro

ss S

ectio

n (a

rb. u

nits

)

k(A-1)

M. Zoppi, M. Celli, A.K. Soper, Phys. Rev. B 58, 11905 (1998)M. Celli, N. Rhodes, A.K. Soper, M. Zoppi, J. Phys. Cond. Matt. 11, 10229 (1999)M. Zoppi, U. Bafile, M. Celli, ... et al.: J. Phys. Cond. Matt. 15, S107 (2003)M. Celli, U. Bafile, ...., M. Zoppi, Submitted to PRB, Oct. 2004.

• meanwhile, from X-ray experiments (ESRF):• G. Pratesi, D. Colognesi...et al.: Philos. Mag. B 82, 305 (2002)• ... G. Pratesi, D. Colognesi...et al.: J. Low Temp. Phys. 129 117 (2002)

microscopic (structure and) dynamics of fluids

D.A.C.

collectiveself

I.R.absorption

neutron scattering

D.I.N.S.

motionspositions

simulation

potentials2-body, 3-body

density analysis

diluted gasesliquids

pressure

incoherent coherent

light scattering

X-ray scattering

TOSCADensity of States

multi-componentsystems

collectivemotions

light scatteringX-ray scatteringneutron scattering

Collective dynamics of fluidsModel

developmentTheory

( ) ( ) ( )∫ ∑ ∑=∞+

∞− = =

⋅⋅−− N

α

N

β

tiitωi βα eeN

edtπ

ωS1 1

0121, RQRQQ

SimulationScattering

experiments

in the case of neutrons

( ) ( )⎭⎬⎫

⎩⎨⎧ += ωS

πσωS

πσ

kk

ωdΩdσd ,

4,

4 sinccoh

0

12

QQ

( ) ( )( )

( )( ) ( )

( )( ) ( ) ⎥

⎥

⎦

⎤

⎢⎢

⎣

⎡

+−

−−+

++

+++

+

−= 222

s

s2

222s

s2

22T

2

2T

21

211,

ΓQQcω

QcωbΓQγΓQQcω

QcωbΓQγQDω

QDγγ

πQSωQS

memory function approach:

Rayleigh-Brillouin

triplet

light scattering

( ) ( ) ( )∫ ′−′′t

ttQFtQMtdtQF0

,, on depends , &&&

M(Q,t) tells how much past history affects the fluid dynamics, and for how earlier time

( ) ( ) ( )QτteQAtQM −=,

•Small Q and ω:

• the fluid “has time” to relax towards equilibrium, with viscous dissipation

•Large Q and ω:

• the fluid behaves as an elastic(disordered) solid

Neutron Brillouin Scattering

With increasing Q we enter a dynamical regime that can be explored with neutrons only:

“neutron Brillouin scattering”or small-angle inelastic coherent scattering

Q ≈ 1 - 10 nm-1 E ≈ 1 meV

U. Bafile et al., PRL 65 , 2394 (1990)Ô / ps-1

S(Í,

Ô) /

ps

S(k,ω

) / p

s

ω / ps-1

←⎯ argon density

X-ray Brillouin scatteringAt slightly larger Q or E, X rays too come into play, thanks to recent advances in high-resolution inelastic scattering

Liquid AluminiumT. Scopigno et al., PRE 63 , 011210 (2000)

Liquid SiliconS. Hosokawa et al., JPCM 15, L623 (2003)

Liquid SodiumT. Scopigno et al., PRE 65 , 031205 (2002)

M. Sampoli et al., PRL 88, 085502 (2002)

MD simulation

“Fast sound”in binary mixtures:

He0.65 - Ne0.35

He-NeU. Bafile et al., PRL 86, 1019 (2001)

neutron scattering

cmix = 400 m/s

cHe = 534 m/s

cmix = 400 m/sP. Westerhuijs et al.: PRA (1992)neutron scattering

microscopic (structure and) dynamics of fluids

D.A.C.

collectiveself

I.R.absorption

neutron scattering

D.I.N.S.

motionspositions

simulation

potentials2-body, 3-body

density analysis

diluted gasesliquids

pressure

incoherent coherent

light scattering

X-ray scattering

TOSCADensity of States

multi-componentsystems

selfmotions

incoherentinelastic

neutron scattering

Main incoherent INS regimes

22motion diffusive

andlow :

QD∆E

EQ

sh=

⇒QENS

)()1)((),(

n correlatio-autovelocity andmedium :

2

EfE

EnQEQS

EQ

Bself

+≈

⇒INS

kEMQ∆E

EQ

32355.2recoil free

andhigh :22h

=⇒

DINS

INS: velocity auto-correlations in H2 and H2+D2

)(Fourier t.(0)(t):

)(fitapprox.Gaussian ),( :

11 Ef

EfEQSself

⇒⇒⋅

⇒⇒⇒

vvSimulation Dynamic Quantum

INS

D. Colognesi, M.Celli, M. Neumann and M. Zoppi, Phys. Rev. E (2004) in press

Extension to solid systems: from LiH to CsH

70 80 90 100 110 120 130 140 1500.00

0.01

0.02

0.03

0.04

0.05

LiH, Optic

Z H(hω

) (m

eV-1)

hω (meV)

DDM13, (Dyck & Jex, 1981) SM-IV, (Verble, Warren & Yarnell, 1968) TOSCA-II (Colognesi et al., 2002)

40 60 80 100 120 140

0.000

0.025

0.050

0.075

0.100

Z H(E

) (m

eV-1)

E (meV)

LiH NaH KH RbH CsH

( )∑ ∑∈ =

−=FBZ

r

jjEj

NEZ

qqqσ

3

1

2HH ),(),(

31)( ωδ h

J. Boronat, C. Cazorla, D. Colognesi, and M. Zoppi, Phys. Rev. B 69, 174302 (2004).

microscopic (structure and) dynamics of fluids

D.A.C.

collectiveself

I.R.absorption

neutron scattering

D.I.N.S.

motionspositions

simulation

potentials2-body, 3-body

density analysis

diluted gasesliquids

pressure

incoherent coherent

light scattering

X-ray scattering

TOSCADensity of States

multi-componentsystems

high pressurescience

I.R. absorptionlight scatteringX-ray scattering

High pressure science

•• Fundamental physics (hydrogen metallization)Fundamental physics (hydrogen metallization)

• Molecular crystals (phase diagrams)

• Polymerization → Metallization

• Mixtures (stoichiometric compounds)

• Earth Physics (internal core, rocks melting ...)

• Planetary atmospheres (Jupiter, Saturn, ... )

• Material science (ultra hard complex materials)

Diamond Anvil Cell

our membrane cell

High pressure HydrogenFree rotor approximation holds up to high pressure: hcp(J is a good quantum number).Increasing pressure:

Freezing of rotational dynamicsOrientational transitions observed at 120-150 GPa(1.2-1.5 Mbar) in para-H2

Eventually,molecular identity is lost ~350 GPa→ metallization

Internuclear distance of hydrogen

0 50 100 150 200 250 3000.73

0.74

0.75

0.76 May et al. 1961 Moulton et al. 1988 Ulivi et al. 1998 free molecule solid low density Loubeyre et al. 1991 this work

Solid5 K

gas297 Kr m

(Å)

density (mol/l)

346 348 350 352 354 356 358 360 362

28.1 nm-3

32.0 nm-3

Inte

nsity

(a.u

.)

Raman shift (cm-1)

• collective rotational excitations

• 3rd order perturbation theory

Rotational Raman Scattering in fluid and solid H2 at room temperature.P= 0 - 20 GPa (0 - 200 kbar): gray dots

L. Ulivi, M. Zoppi, L. Gioè, G. Pratesi, Phys. Rev. B58, 2383, (1998)

Solid hcp:

F. Grazzi, M. Moraldi, L. Ulivi, Europhys. Lett. in press

stoichiometric compounds:Ar(H2)2, Ne (He)2, CH4 (H2)2, He(N2)11 , ...

Almost free rotation of hydrogen molecule

300 400 500 600 700

S0(1)S0(0)

6 GPa30 K

Frequency shift (cm-1)8 hydrogen molecules per unit cellL. Ulivi, R. Bini, P. Loubeyre, R. LeToullec, H. Jodl: Phys. Rev. B 60 6502 (1999)F Grazzi & L Ulivi Europhys Lett 52 564 (2000)

Rotons in Ar(H2)2 – anisotropic potential

2 3 4 5 6

-0.5

0.0

Inte

ract

ion

ener

gy (c

m-1)

Intermolecular distance (Å)

0.1

1

10

100

Norman-Watts-Buck Diep-Johnson Schaefer- Köhler this work

V202

V224

H2-H2

250 300 350 400 450 500 550

Frequency (cm-1)

P=14 GPa

F. Grazzi, M. Santoro, M. Moraldi, L. Ulivi,. P. R. L. 87, 125506 (2001)F. Grazzi, M. Santoro, M. Moraldi, L. Ulivi, P. R. B 66 144303 (2002)

Solid Oxygen: x-ray diffraction (ESRF)

•• Only the Only the αα phase phase exists at low exists at low PP andand TT

Molecule association:Molecule association:SpectroscopySpectroscopy

MagnetiMagnetic Properties:c Properties:SpeSpecctroscoptroscopyyNeutron DNeutron Diffraiffractionction

F. Gorelli, M. Santoro, L. Ulivi, M. Hanfland Phys. Rev. B 65 172106 (2002)

IR absorption in the ε-phase

100 200 300 400 500 6000.00.20.40.60.81.0

νFIRε−phase

295 KGPa

48

4337

3126.618.1

10.5

11.7

14.7

Abso

rban

ce

Frequency (cm-1)

O2 + O2 → O4

F. Gorelli, L. Ulivi, M. Santoro, R. BiniPhys. Rev. Lett. 83 4093 (1999)Phys Rev B63 104110 (2001)

Physics Today, Dec. 1999 p.9

Solid oxygen: magnetic properties

1500 1600 1700 18000.0

0.2

0.4

2.55.1

6.6

23 K

Abs

orba

nce

Frequency (cm-1)

0.0

0.5

1.0

1.5ε−phaseP (GPa)

7.5

8.0

0

200

400

0 5 10

T

Pαα'? δ'?

δ

γ β

fluid

IR absorption:• The evidence of a

forbidden vibrationalexcitation is induced by the magnetic interactionwhich doubles the elementary cell.

F. Gorelli, L. Ulivi, M. Santoro, R.Bini,Phys. Rev. B62, R3604 (2000).

Solid oxygen: high pressure neutron diffraction

Experiment:LLB, G6.1sapphire anvil cell

Different magnetic order betweenα− and δ−phase

I.N. Goncharenko, O.L. Makarova, L. Ulivi, Phys. Rev. Lett. 93, 055502 (2004)

Prospettive a medio-lungo termine :sistemi complessi

Prospettive a breve termine:• Immagazzinamento dell’Idrogeno (EU-FP6)

– materiali nanoporosi (nanotubi di carbonio)– idruri metallici (diagnostica neutronica)– idruri metallorganici (neutroni, luce, H.P.)

• Strumentazione neutronica avanzata– Progetto INES (in fase di completamento)– Progetto NIMROD (EU-FP6)

H-storage in carbon nanotubes:where is hydrogen?

Internal site

External surface External channel

Interstitiale site

neutron diffraction experimentSANDALS @ ISIS

0 1 2 3 4 5 6 7 8 9 100.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2 empty nanotubes nanotubes + D2

DC

S

Q(A-1)

From the differences in the two diffraction patterns we will obtain information on the C-D correlation.

CNR-CCLRC international cooperation• 1991-1995 SERC-CNR agreement for access to ISIS

5% utilization level:- (4%) Access + (1%) Instrument: PRISMA

• 1996-2001 First renewal (CCLRC-CNR)5% utilization level:- (4%) Access + (1%) Instrument: TOSCA

• 2001-2004 Italian Neutron Experimental Station(INES)50% utilization level for CNR(in progress, commissioning early 2005)

• 2002-2008 Second renewal (CCLRC-CNR)4% utilization level:- (3%) Access +(1%) Instrument: NIMROD

The TOSCA project (1996-2001)

CNR investment3.2 GLit. = 1% of ISIS

An international cooperation between CNR and CCLRC(UK)ISIS pulsed neutron sourcewww.ifac.cnr.it/tosca/tosca-main.htm

The INES project (2001-2004)

Within the framework of the international cooperation between CNR and CCLRC(UK)ISIS pulsed neutron sourcewww.ifac.cnr.it/ines/ines-main.htm

•CNR investment:600 keuro.

•reserved utilization:50 % for Italians

The NIMROD project (2004-2008)

Within the framework of the international cooperation agreement (2002-2008) between CNR and CCLRC for the utilization of the ISIS pulsed neutron source

CNR investment1560 k-euro ~ 1% ISIS

grazie della vostra attenzione !