of 3
Supporting Information for:
Mechanisms of Failure in Nanoscale Metallic Glass
X. Wendy Gu
, Mehdi Jafary-Zadeh ̊, David Z. Chen
, Zhaoxuan Wu ̊, Yong-Wei Zhang ̊, David
J. Srolovitz
+
, Julia R. Greer
*
Division of Chemistry and Chemical Engineering, and
Division of Engineering and Applied
Science, California Institute of Technology, 1200 E
. California Blvd., Pasadena, CA 91125,
United States
̊Institute of High Performance Computing, 1 Fusiono
polis Way, #16-16 Connexis, Singapore
138632
+
Departments of Materials Science and Engineering &
Mechanical Engineering and Applied
Mechanics, University of Pennsylvania, Philadelphia
, PA 19104, United States
CORRESPONDING AUTHOR:
Julia R. Greer
M/C 309-81, Division of Engineering and Applied Sci
ence, California Institute of Technology,
1200 E. California Blvd., Pasadena, CA 91125, Unite
d States
626-395-4127
jrgreer@caltech.edu
TEM sample preparation
TEM samples of notched and unnotched metallic glass
nano-cylinders were prepared
through a focus ion beam (FIB) free process that re
sulted in minimal damage to the
nanostructures. Nano-cylinders with poor adhesion t
o the growth substrate were attached using
Van der Waals forces to a custom-fabricated tungste
n needle attached to the indenter tip in the
InSEM, an in-situ scanning electron microscope (SEM
) nanomechanical testing instrument
(Nanomechanics, Inc.). The W needle was used as a m
icromanipulator. Efforts were made to
contact the W needle to the portion of the pillar b
etween the lowest notch and the substrate, so
that the notches would not be deformed during TEM p
reparation. The W needle carrying the
pillar is then moved to the Cu TEM grid, and the pi
llar is glued to the TEM grid using carbon
deposition using the SEM electron beam. The W needl
e is then removed from the pillar. A small
amount of W is applied to the cap of the pillar, fa
r from the notches in the gauge section, using
deposition by electron beam (FEI Nova 200 Dual Beam
) in order to secure the pillar to the TEM
grid.
Molecular dynamics simulations
Simulations were conducted using the Large-Scale At
omic/Molecular Massively Parallel
Simulator (LAMMPS)
1
. The simulation samples were prepared from a melti
ng-and-quenching
simulation of a randomly substituted Fe
75
P
25
solid solution whereby a Fe
75
P
25
rectangular prism
with periodic boundary conditions (PBC) in all dire
ctions was melted at 2000 K and equilibrated
for 1 ns. Then, the sample was quenched to 1 K at a
cooling rate of 0.5 Kps
-1
. The time step for
the melting-and-quenching was chosen to be 0.002 ps
, and the isothermal-isobaric ensemble
(NPT) was employed to maintain the pressure of the
system at zero. The Verlet algorithm
2
and
the Nose-Hoover thermostat/barostat
3,4
were used to integrate the equations of motion. Af
ter
quenching, cylindrical nanocylinders were cut from
the quenched bulk metallic glass. The
samples were relaxed using the conjugate gradient (
CG) minimization technique
5
as
implemented in LAMMPS. The nanocylinders were then
equilibrated at the temperature of the
tensile test (1 K) and zero pressure for 0.5 ns usi
ng the NPT ensemble. Uniaxial tensile loading
was applied to the nanocylinders by rescaling the s
imulation box and a time step of 0.001 ps.
During tensile loading, the PBC was applied just al
ong the loading direction, and the temperature
of the system was maintained at 1 K, which reduces
the thermal fluctuation effects and facilitates
the analyses of atomic quantities
6
. A strain rate of 5 x 10
7
s
-1
was applied during tensile testing.
Supplementary movies
Movie S1.
In-situ
SEM video of an electroplated NiP metallic glass s
ample with diameter of
~75 nm tested in tension.
Movie S2.
In-situ
SEM video of a notched, electroplated NiP metallic
glass sample with
diameter of ~70 nm tested in tension.
Movie S3. Molecular dynamics movie of the tensile d
eformation of a FeP metallic glass with
a diameter of 40 nm. The cross-section of the sampl
e is shown, and the von Mises strain is
plotted in the video.
Movie S4. Molecular dynamics movie of the tensile d
eformation of a notched FeP metallic
glass with a diameter of 40 nm. The cross-section o
f the sample is shown, and the von
Mises strain is plotted in the video.
References
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J. Comput. Phys.
1995
,
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, 1-19.
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Phys. Rev.
1967
,
159
, 98-103.
(3) Nosé, S.
The Journal of Chemical Physics
1984
,
81
, 511-519.
(4) Hoover, W. G.
Phys. Rev. A
1985
,
31
, 1695-1697.
(5) Štich, I.; Car, R.; Parrinello, M.; Baroni, S.
Phys. Rev. B
1989
,
39
, 4997-5004.
(6) Murali, P.; Guo, T. F.; Zhang, Y. W.; Narasimha
n, R.; Li, Y.; Gao, H. J.
Phys. Rev. Lett.
2011
,
107
, 215501.