Surface Melting(faceting?)

Sergio Calatroni

Surface Melting

Sergio Calatroni 2

(110) -> 1270 K (1000 C)(100) -> 1290 K (1020 C)(111) -> 1310 K (1040 C)

Bulk fusion -> Lindemann criterion: rms thermal vibration amplitude of the solid reaches some 14% of the nearest-neighbour distance.In a surface atoms are closer together than in bulk -> lower melting point

Stress effect

Sergio Calatroni 3

Cluster size effect

Sergio Calatroni 4

MD from Kai Nordlund

Sergio Calatroni 5

2 ns

~10 nm

Faceting

Sergio Calatroni 6

Faceting happens:• Vacuum 1040 C

• Does not happen:• 1 bar H2 SLAC 1040 C• 1 mbar H2 CERN 1040 C• 10 mbar H2 CERN 850 C

What orientations?

Hydrogen + Cu

Sergio Calatroni 7

1083 C

P = 500 bar!

Missing info: effect of H2 on surface melting

+H

+H

(Cu)+H / L+H

1.00E-02 1.00E-01 1.00E+00 1.00E+01 1.00E+02 1.00E+03 1.00E+040.0000001

0.000001

0.00001

0.0001

0.001

0.01

0.1

1

Concentration 700 K [H in %]

Concentration 1000 K [H in %]

Concentration 1300 K [H in %]

Concentration 1356 K [H in %]

Concentration 1356 K [H in %]

Concentration 1600 K [H in %]

Pressure [mbar]

Conc

entr

ation

ato

mic

%Hydrogen solubility in Cu

Sergio Calatroni 8

CERN SLAC

liquid

solid

700 K

1000K

1356K

1356K1600K

0.2%

90 bar