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A solid-state physicist's journey to the centers of planets
Sandro Scandolo (ICTP, Trieste, Italy)
Physics Colloquium @ Univ. Pavia, April 2020
A solid-state physicist's journey to the centers of planets Sandro - - PowerPoint PPT Presentation
A solid-state physicist's journey to the centers of planets Sandro - - PowerPoint PPT Presentation
A solid-state physicist's journey to the centers of planets Sandro Scandolo (ICTP, Trieste, Italy) Physics Colloquium @ Univ. Pavia, April 2020 Diamond Graphite P ~ 14 GPa (room T) P ~ 6 GPa (2000 K) How do diamonds form? Sca Sca
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How do diamonds form?
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Sca Scandolo & & Je Jeanloz, z, Ame Ameri rica can Sci Scientist st 2003 Sca Scandolo & & Je Jeanloz, z, Ame Ameri rica can Sci Scientist st (2 (2003) )
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Earth-like Jupiter-like Neptune-like
Exoplanets
- H. Rauer (TU Berlin)
Queloz & Mayor, Nobel Physics 2019
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Sca Scandolo & & Je Jeanloz, z, Ame Ameri rica can Sci Scientist st (2 (2003) )
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1955:
The first man-made diamonds
General Electrics
1946:
Nobel to Percy Bridgman
High pressure: the early days
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Shock waves Diamond anvil cell
High pressure: today
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Sca Scandolo & & Je Jeanloz, z, Ame Ameri rica can Sci Scientist st (2 (2003) )
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Quantum m si simu mulations: s: The “st “standard rd mo model”
Hψ = Eψ
Sch Schro roedinger r equation for r elect ctro rons s “Mo “Molecu cular r dyn ynami mics” cs” for r atoms ms
Ma = F = -dE/dR
“Ab “Ab-i
- initio”
” mo molecu cular r dyn ynami mics cs = = Classi ssica cal mo molecu cular r dyn ynami mics cs in the potential energ rgy y su surf rface ce genera rated by y the elect ctro rons s in their r quantum m gro round st state
Electron charge density in SiO2 stishovite
- R. Cohen
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Walter Kohn (1923-2016)
Nobel prize in Chemistry 1998 (for work done in the 60’s) The energy E[ρ(x)] of a collection of electrons is a unique functional of the electron density ρ(x)
Density-functional theory
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Ab-initio molecular dynamics
http://www.quantum-espresso.org
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Graphite-Diamond transition
F.P. Bundy, Physica A 156, 169 (1989)
Transformation path from graphite to hex diamond uncovered by ab-initio molecular dynamics
Scandolo et al,
- Phys. Rev. Lett. 1995
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Non-molecular CO2
SiO2 CO2
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+ Molecular CO2 tranforms into a silica-like
crystal at about 50 GPa + Silica-like phases of CO2 predicted to be ultrahard
Molecular CO2 Candidate theoretical structures for silica-like CO2 Serra, Cavazzoni, Chiarotti, Scandolo, Tosatti, Science 284, 788 (1999)
Disappearance of molecular peaks Formation of C-O-C bonds Experimental confirmation of silica-like CO2
Yoo et al, Science 283, 1510 (1999)
Non-molecular CO2
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Non-molecular CO2: β-cristobalite confirmed
20 GPa X-ray diffraction IR spectroscopy Sample laser-heated with CO2 laser
Santoro, Gorelli, Bini, Haines, Cambon, Levelut, Montoya, Scandolo, PNAS 2012
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Water and methane at planetary conditions
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60% molar fraction
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phase diagram of water from first principles
- C. Cavazzoni et al., Science 283, 44 (1999)
Experimental confirmation (?)
- f superionic phase:
- A. Goncharov et al.,
- Phys. Rev. Lett. (2006)
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Su Superi rionic c Water r
P P = = 150 GPa Pa T = = 2500 K K
Proton diffusion by hopping Oxygen sublattice remains crystalline
- C. Cavazzoni et al., Science 283, 44 (1999)
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H2O+CH CH4+NH3 Marvin Ross, “Diamonds in the sky” Nature (1981) Methane was found to dissociate under a shock wave
Sca Scandolo & & Je Jeanloz, z, Ame Ameri rica can Sci Scientist st (2 (2003) )
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Dissociation of methane at extreme (planetary) conditions
- F. Ancilotto et al.,
Science 275, 1288 (1997)
Compressed methane Compressed methane after heating to 4000 K
L.R. Benedetti et al., Science 283, 100 (1999)
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92% molar fraction
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CH4 / H2O mixtures at extreme conditions
92% of the Uranus and Neptune ice layer Fluid inclusions, abiogenic formation of methane Prototype of hydrophobic interactions How corrosive is ionized water? Methane hydrate clathrates SIMULATIONS: 26 CH4 + 38 H2O at 4 different P-T
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Methane / water mixture at 50 GPa
Fast proton diffusion by proton hopping between adjacent molecules Methane “attacked” by ionized water Occasional formation of C-O bonds No formation of longer hydrocarbons (C-C bonds) M.-S. Lee and S. Scandolo, Nature Comm. 2011
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>90% molar fraction
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E.
- E. Wigner
r and H.B.
- B. Huntington
“O “On the possi ssibility y of a me metallic c mo modifica cation of hyd ydro rogen” ” J.
- J. Chem.
- m. Ph
Phys.
- ys. 3, 764 (1
(1935) )
Heml mley y and Ma Mao, Rev v Mo Mod Ph Phys ys
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? ?
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- At
At which ch depth does s hyd ydro rogen beco come me an elect ctri rica cal co conduct ctor? r?
- Is
s me metalliza zation acco ccomp mpanied by y a sh sharp rp densi sity y ch change?
?
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Mo Molecu cular r to non-mo
- molecu
cular r tra ransi sition
S.
- S. Sca
Scandolo, Pro Proc.
- c. Natl. Aca
- Acad. Sci
- Sci. USA,
SA, 2003
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Silvera et al, PRB 2016, PNAS 2016
2002 2004 2010
X
Metallic hydrogen
January 2017
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Take-home message
“Ab-initio Molecular Dynamics” is the most powerful theoretical tool to study atomic dynamics Atomic diffusion, vibrations, phase transitions, chemical reactions, structural determination, thermal transport, etc… Advantages: ✔ any chemical species, with chemical accuracy ✔ availability of open source codes Limitations: ✖ a few hundred atoms, up to 100 picoseconds ✖ large computational resources
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