Post on 27-Jun-2020
Progetto CRESCOCatania, 11.2.09
Massimo Celino ENEA, Dipartimento Tecnologie Fisiche e Nuovi MaterialiC. R. Casaccia, Rome, Italycelino@casaccia.enea.it
M. Celino and S. Giusepponi
Materials for hydrogen storage:ab-initio Molecular Dynamics study in the ENEA-GRID environment
ENEAItalian Agency for New Technologies, Energy and EnvironmentPhysical Technologies and New Materials DepartmentCasaccia Research CentreRome, Italy
Progetto CRESCOCatania, 11.2.09
Massimo Celino ENEA, Dipartimento Tecnologie Fisiche e Nuovi MaterialiC. R. Casaccia, Rome, Italycelino@casaccia.enea.it
• It can store significant quantities of hydrogen (7.7 wt% of hydrogen)
• Low cost of production• High abundance
Introduction: MgH2
• Too high temperature of decomposition • Slow decomposition kinetics
BUT
Progetto CRESCOCatania, 11.2.09
Massimo Celino ENEA, Dipartimento Tecnologie Fisiche e Nuovi MaterialiC. R. Casaccia, Rome, Italycelino@casaccia.enea.it
Improvements comes from:
Introduction: MgH2
Adding small amounts of catalytic metals
High energy ball milling• High density of crystal
defects• Fine dispersion of
second phase particles
Progetto CRESCOCatania, 11.2.09
Massimo Celino ENEA, Dipartimento Tecnologie Fisiche e Nuovi MaterialiC. R. Casaccia, Rome, Italycelino@casaccia.enea.it
Now the problem is to control at the atomic level the phase transformation of the milled samples
Experimental results
Progetto CRESCOCatania, 11.2.09
Massimo Celino ENEA, Dipartimento Tecnologie Fisiche e Nuovi MaterialiC. R. Casaccia, Rome, Italycelino@casaccia.enea.it
It is possible to perform SEM observation at high spatial resolution of the phasesdistribution in partially decomposed Mg-MgH2 containing heavier catalyzing particles
Mg/MgH2 Fe (10%)10h milledMg/MgH2 10h milled
Mg
MgH2
Fe
Experimental results
The addition of Fe particles induces a nucleation process diffused in the material giving raise to a strongly interconnected microstructure
Thanks to A. Montone, ENEA
Progetto CRESCOCatania, 11.2.09
Massimo Celino ENEA, Dipartimento Tecnologie Fisiche e Nuovi MaterialiC. R. Casaccia, Rome, Italycelino@casaccia.enea.it
Molecular Dynamics Simulations
{ }( )iii xV
dtdxm −∇=2
2
N atoms3N degrees of freedom
New atomic positions
output
input
Distances among the atoms
t=1,Tmax
Forces among all the atoms
Compute physical quantities
Data storage
Progetto CRESCOCatania, 11.2.09
Massimo Celino ENEA, Dipartimento Tecnologie Fisiche e Nuovi MaterialiC. R. Casaccia, Rome, Italycelino@casaccia.enea.it
0
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400
0 10 20 30 40 50 60 70
0
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0 50 100 150 200 250 300
IBM SP5
CRESCO
Mesh: 72x576x180
Time Speedup
Processing Elements
Processing Elements
CPMD: code performance
Progetto CRESCOCatania, 11.2.09
Massimo Celino ENEA, Dipartimento Tecnologie Fisiche e Nuovi MaterialiC. R. Casaccia, Rome, Italycelino@casaccia.enea.it
CPMD: code performance
0
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0 200 400 600 800 1000
Rotate system:
mesh 576 on x axisSpeedup
Processing elements
IBM SP5: ~ 8 sec - 64 PE
CRESCO: ~ 8 sec – 150 PE ~ 3 sec – 576 PE
Progetto CRESCOCatania, 11.2.09
Massimo Celino ENEA, Dipartimento Tecnologie Fisiche e Nuovi MaterialiC. R. Casaccia, Rome, Italycelino@casaccia.enea.it
Hydrogen desorption: the MgH2-Mg interface
Starting configuration
Mg surface
MgH2surface
InterfaceLx= 6.21 Å
Ly= 50.30 Å
Lz= 15.10 Å
MgH2:60 Mg atoms + 120 H atoms
IdrogenoMagnesio
Mg: 72 atoms
Progetto CRESCOCatania, 11.2.09
Massimo Celino ENEA, Dipartimento Tecnologie Fisiche e Nuovi MaterialiC. R. Casaccia, Rome, Italycelino@casaccia.enea.it
Molecular dynamics at T= 700 K
Starting configuration
T= 700 K
Progetto CRESCOCatania, 11.2.09
Massimo Celino ENEA, Dipartimento Tecnologie Fisiche e Nuovi MaterialiC. R. Casaccia, Rome, Italycelino@casaccia.enea.it
Molecular dynamics (NVT ensemble)
Starting configuration
T= 700 K
T= 800 K
T= 900 K
Progetto CRESCOCatania, 11.2.09
Massimo Celino ENEA, Dipartimento Tecnologie Fisiche e Nuovi MaterialiC. R. Casaccia, Rome, Italycelino@casaccia.enea.it
Starting configuration with a Fe atom near the interface:
• Increase of Hydrogen mobility • Lower desorption temperature
Fe
Mg-MgH2 interface : Fe
T= 500 K
Fe in POS 1
Progetto CRESCOCatania, 11.2.09
Massimo Celino ENEA, Dipartimento Tecnologie Fisiche e Nuovi MaterialiC. R. Casaccia, Rome, Italycelino@casaccia.enea.it
Fe in POS 2
Fe in POS 3
Mg-MgH2 interface : Fe
Progetto CRESCOCatania, 11.2.09
Massimo Celino ENEA, Dipartimento Tecnologie Fisiche e Nuovi MaterialiC. R. Casaccia, Rome, Italycelino@casaccia.enea.it
T= 500 K
Fe in POS 1
Fe in POS 2
Fe in POS 3
Mg-MgH2 interface : Fe
Progetto CRESCOCatania, 11.2.09
Massimo Celino ENEA, Dipartimento Tecnologie Fisiche e Nuovi MaterialiC. R. Casaccia, Rome, Italycelino@casaccia.enea.it
T= 400 KFe in POS 1
Fe in POS 2
Fe in POS 3
Mg-MgH2 interface : Fe
Progetto CRESCOCatania, 11.2.09
Massimo Celino ENEA, Dipartimento Tecnologie Fisiche e Nuovi MaterialiC. R. Casaccia, Rome, Italycelino@casaccia.enea.it
T= 400 K POS 2
Mg-MgH2 interface : Fe
Fe atom: first and second shellof Mg coordination
Progetto CRESCOCatania, 11.2.09
Massimo Celino ENEA, Dipartimento Tecnologie Fisiche e Nuovi MaterialiC. R. Casaccia, Rome, Italycelino@casaccia.enea.it
T= 400 K
POS 3
Mg-MgH2 interface : Fe
Progetto CRESCOCatania, 11.2.09
Massimo Celino ENEA, Dipartimento Tecnologie Fisiche e Nuovi MaterialiC. R. Casaccia, Rome, Italycelino@casaccia.enea.it
Conclusions
• It is possible to characterize experimentally and numerically the hydrogen desorption from MgH2
• The addition of catalyzing particles induces a nucleation process diffused in the material giving raise to a strongly interconnected microstructure
• The interplay of interfaces and catalyzing particles lowers Hydrogen desorption temperature: Fe atoms induce a depression region able to lower the bonding between H and Mg