Tetracyanomethane under Pressure: Extended CN Polymers from Precursors with Built-in sp3 Centers

Article abstract of DOI:10.1021/acs.jpca.7b10729

Tetracyanomethane, C(CN)₄, is a tetrahedral molecule containing a central sp³ carbon that is coordinated by reactive nitrile groups that could potentially transform to an extended CN network with a significant fraction of sp³ carbon. High-purity C(CN)₄ was synthesized, and its physiochemical behavior was studied using in situ synchrotron angle-dispersive powder X-ray diffraction (PXRD) and Raman and infrared (IR) spectroscopies in a diamond anvil cell (DAC) up to 21 GPa. The pressure dependence of the fundamental vibrational modes associated with the molecular solid was determined, and some low-frequency Raman modes are reported for the first time. Crystalline molecular C(CN)₄ starts to polymerize above ～7 GPa and transforms into an interconnected disordered network, which is recoverable to ambient conditions. The results demonstrate feasibility for the pressure-induced polymerization of molecules with premeditated functionality.

Full text of DOI:10.1021/acs.jpca.7b10729

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Article
Tetracyanomethane Under Pressure: Extended CN
3
Polymers from Precursors with Built-in sp Centers
Derek W. Keefer, Huiyang Gou, Qianqian Wang, Andrew P. Purdy, Albert Epshteyn,
Stephen J. Juhl, George D Cody, John V. Badding, and Timothy A. Strobel
J. Phys. Chem. A, Just Accepted Manuscript • DOI: 10.1021/acs.jpca.7b10729 • Publication Date (Web): 12 Feb 2018
Downloaded from http://pubs.acs.org on February 17, 2018
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Tetracyanomethane Under Pressure: Extended CN Polymers from
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Precursors with Built-in sp Centers
†
,*
‡,||
‡
§
§
Derek W. Keefer , Huiyang Gou , Qianqian Wang , Andrew Purdy , Albert Epshteyn , Stephen
†
‡
†,#,ꢀ,◊
‡,*
J. Juhl , George D. Cody , John Badding
, Timothy A. Strobel
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Department of Chemistry, Department of Physics, Department of Materials Science and
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Engineering, and Materials Research Institute, The Pennsylvania State University, University
Park, PA 16802, USA.
‡
Geophysical Laboratory, Carnegie Institution of Washington, 5251 Broad Branch Road NW,
Washington, DC, 20015, USA
§
Naval Research Laboratory, Chemistry Division, 4555 Overlook Ave., SW, Washington, DC,
20375, USA.
||
Center for High Pressure Science and Technology Advanced Research, Beijing 100094, China.
*keefer.derek@gmail.com
*tstrobel@ciw.edu
ABSTRACT
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Tetracyanomethane, C(CN) , is a tetrahedral molecule containing a central sp carbon that is
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coordinated by reactive nitrile groups that could potentially transform to an extended CN
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network with a significant fraction of sp carbon. Highꢁpurity C(CN) was synthesized and its
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physiochemical behavior was studied using in situ synchrotron angleꢁdispersive powder Xꢁray
diffraction (PXRD) and Raman and Infrared (IR) spectroscopies in a diamond anvil cell (DAC)
up to 21 GPa. The pressure dependence of the fundamental vibrational modes associated with the
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molecular solid was determined and some lowꢁfrequency Raman modes are reported for the first
time. Crystalline molecular C(CN) starts to polymerize above ~7 GPa and transforms into an
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interconnected disordered network, which is recoverable to ambient conditions. The results
demonstrate feasibility for the pressureꢁinduced polymerization of molecules with premeditated
functionality.
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INTRODUCTION
The carbonꢁnitrogen (CN) system has many similarities with the pure carbon. For example, both
systems possess (or are predicted to possess) twoꢁdimensional, soft allotropes (graphite and
graphitic carbon nitride), as well as threeꢁdimensional, superhard allotropes (diamond and cubic
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carbon nitride). The structural dimensionality and resulting physical properties are directly
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determined by the degree to which bonding hybridization takes on sp and/or sp forms. For CN
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materials, several techniques have been demonstrated for the synthesis of sp materials, however,
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significant challenges remain to produce threeꢁdimensional extended materials with sp
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hybridization.
There are several approaches to synthesize carbon nitride extended solids, such as soft chemical
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methods, magnetron sputtering, highꢁpressure techniques, etc. Generally, sp hybridized
graphitic C N (gꢁC N ), which is considered to be a promising lowꢁcost, metalꢁfree, visibleꢁ
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lightꢁactive photocatalyst, can be synthesized through chemical methods, such as thermal
condensation of nitrogenꢁrich and oxygenꢁfree compounds containing CꢁN core structures (e.g.
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cyanamide, dicyandiamide, melamine, thiourea, or urea).
Amorphous or fullereneꢁlike CNx
thin films are typically fabricated by magnetron sputtering methods with interesting mechanical
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properties, such as high hardness and elastic recovery.
Incorporation of nitrogen is
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considered to be helpful for the formation of fullereneꢁlike microstructure and the crossꢁlinking
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between graphitic layers by sp coordinated carbon in the carbon nitride films that contribute to
the high hardness and elastic recovery. High pressure is also an alternative method to produce
carbon nitride solids, such as the polymerization of different highꢁenergy, unsaturated molecules
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under pressure.
In most highꢁpressure studies, amorphous sp bonded carbon nitride is
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obtained with some sp bonded carbon. The recent highꢁpressure synthesis of crystalline
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orthorhombic CN and tetragonal C N phases with sp hybridization show promise for the
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formation new superhard materials and bonding motifs that span three dimensions.
An
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alternative approach to achieving CN solids with an increased fraction on sp bonds could be to
start with inherently threeꢁdimensional precursor molecules that could be designed to react to
form extended networks. In this case, the reaction process would occur in the bulk and samples
might be scalable in quantities beyond that which is possible for thin films.
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Tetracyanomethane was originally synthesized and characterized by Mayer in ca. 1968. Since
cyanogen chloride is not commercially available, we used cyanogen bromide instead, and
obtained C(CN) in about 50% yield. The molecule has tetrahedral symmetry and contains a
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central sp carbon that is coordinated by reactive nitrile groups that could potentially transform to
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a hydrogenꢁfree, threeꢁdimensional extended CN network with a significant fraction of sp
carbon. It is well established that cyanide groups can undergo both thermallyꢁactivated and/or
pressureꢁinduced polymerization reactions, however, starting precursor molecules generally lack
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D / intrisic sp character, and the resulting extended CN phases are typically sp , even under
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elevated pressure conditions.
In this study, we examine the behavior of C(CN) under compression using Raman, IR and
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PXRD up to 20 GPa and test the hypothesis of whether extended 3D networks can be produced
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by reaction of a 3D precursor. Raman and IR spectroscopy provide in situ information on how
the bonding develops, while synchrotron PXRD was used to monitor how the structure
progresses. Ex situ electron microscopy measurements were performed to establish
characteristics of the recovered product.
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EXPERIMENTAL METHODS
A solution of AgNO (7.19 g, 42.3 mmol) in 70 g H O was added to a solution of KC(CN)
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Strem, 5.40 g, 41.8 mmol) in 65 g H O with vigorous stirring, and was allowed to stir for 12 h.
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The mixture was filtered, and the white solid washed with water and alcohol and pumped dry
while heating with warm water for several hours. AgC(CN) (7.90g, 95%) was isolated.
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Cyanogen bromide (2.50 g, 23.6 mmol) was transferred under vacuum onto AgC(CN) (3.42 g,
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7.3 mmol) in a large Pyrex tube. The tube was sealed under vacuum and immersed in a 100 °C
oil bath for 11 days. The tube was opened in the drybox and the contents were sublimed under
dynamic vacuum using a 100 °C oil bath and an iceꢁcooled cold finger. A total of 1.081 g
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C(CN) was isolated (54%). NMR: (CD CN) C δ 103.2 (C≡N), 22.7 (C). Tetracyanomethane is
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very water sensitive and was handled only in the dry box.
Sample Preparation
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Samples of tetracyanomethane were ground to a fine powder (<1 micron) using an agate mortar
within an argon glove box (O < 0.5 ppm, H O < 0.5 ppm). This powder, with the addition of a
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ruby sphere, was placed into a DAC gasket chamber with culet sizes ranging between 300ꢁ500
µm. A rhenium gasket was prepared by preꢁindention to a thickness between 50ꢁ70 µm. A ~150ꢁ
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90 µm hole was drilled into the center of the indentation, which served as the chamber for the
sample. By measuring the florescence of the ruby sphere, the pressure inside the sample chamber
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could be determined. In most runs, a pressure transmitting medium was not used, but dry
potassium bromide was used to dilute samples for some of the IR runs to avoid absorbance
saturation. To prevent reaction/contamination with moisture in air, all samples were sealed inside
the glove box at a minimum pressure of 0.1 GPa.
Raman
Raman spectra were collected in the backꢁscattered geometry with excitation from a 532 nm
diode laser. The light was focused through a 20× long working distance objective (NA=0.40) and
collected through a 50 µm confocal pinhole and two narrowꢁband notch filters (Ondax). A
Princeton Instrument spectrograph SP2750 (Trenton, NJ) with 1800 or 300 gr/mm grating and a
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liquidꢁnitrogenꢁcooled CCD was used to collect data with a spectral resolution of <2 cm . Neon
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emission lines were used to calibrate the spectrometer to an accuracy of <1 cm . To avoid
damaging the sample, laser power was kept below 5 mW and exposure times were varied up to
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00s. At higher laser power, it was observed that the laser could help promote reaction progress
at high pressure.
Infrared
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MidꢁIR absorption from 600ꢁ4000 cm was collected on a Varian 670ꢁIR spectrometer. A
Globar source was used to generate IR light, which was then focused through a pair of reflecting
objectives. The signal was detected using a liquidꢁnitrogenꢁcooled HgCdTe detector. After the
data were collected, the same DAC was decompressed, the diamonds were cleaned and reference
spectra were collected.
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X-ray diffraction
Powder Xꢁray diffraction (PXRD) data were obtained at the HighꢁPressure Collaborative Access
Team (HPCAT), beamline 16ꢁIDB, of the Advanced Photon Source (APS), Argonne National
Laboratory. Data were collected with a monochromatic beam with a wavelength of 0.4066 Å and
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focused to ~5×7 µm spot. Diffraction data were recorded using a MARCCD and the images
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were processed using the FIT2D(v12.077) data analysis program. Lattice parameters were
obtained through fullꢁprofile fitting using the Le Bail method, as implemented in GSAS with
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EXPGUI.
Scanning and Transmission Electron Microscopy
The recovered samples within the Re gaskets were mounted on an Al stub for chemical
composition mapping and microstructural analysis using a field emission scanning electron
microscope (FEꢁSEM; JEOL JSM 6500F) operating at 15 kV and 1.5 nA. Compositional
analyses were determined by energyꢁdispersive Xꢁray spectroscopy (EDS) using graphite and
BN standards.
Transmission electron microscope (TEM) brightfield imaging was performed using a JEOL 2010
microscope with a LaB electron source operating under an accelerating voltage of 200 kV.
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Samples were carefully removed from the Re gasket using a steel needle, mechanically crushed
on a piece of Teflon, then dispersed onto a silicon monoxide grid with ethanol.
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RESULTS AND DISCUSSION
Tetracyanomethane is a molecular solid at ambient conditions and was previously reported to
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crystallize in a trigonal lattice with space group R3c (No. 161) with six formula units per unit
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cell. The crystal structure may be viewed as a distortion from cubic symmetry due to the weak
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intermolecular interactions that benefit from the denser trigonal structure. Tetracyanomethane
molecules maintain tetrahedral symmetry in the solid phase. The molecules are stacked with the
nitrile groups pointing towards the central carbon of an adjacent molecule along the c axis.
Figure 1 shows the crystal structure C(CN) with nearest neighbor interaction distances. There
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are several short intermolecular distances near 3 Å (3.00, 3.05, 3.10, 3.19 Å) between the
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nitrogen atoms and nitrile carbon atoms of neighboring molecules.
Figure 1. Crystal structure of C(CN) with nearest neighbor interactions shown as red dashed lines. Every
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C/N nitrile atom has three interactions with adjacent molecules near 3.0 Å.
PXRD patterns obtained from our starting material at 0.1 GPa were readily refined using the
trigonal structural model and the resulting lattice parameters of a = 8.951(2) Å and c = 11.54(4)
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Å are in good agreement with the previously reported results at ambient conditions. Figure 2
shows the trends in the PXRD patterns as the material was compressed up to 20 GPa. With
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increasing pressure, the Bragg peaks broaden due to nonꢁhydrostatic compression and
anisotropic microstrain (no pressure medium was used), yet no structural phase transition was
observed and we were able to reliably refine the trigonal lattice parameters up to a pressure of
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4.7 GPa. The lattice parameters a and c both decrease in a manner that is typical for a molecular
solid. The pressureꢁvolume relationship (Fig.2b) was fitted using the thirdꢁorder Birchꢁ
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Murnaghan equation of state (EoS) with a bulk modulus of K = 4.4(3) and derivative of K =
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8(1). Above 14.7 GPa the diffraction intensity decreases drastically and the material appears to
be amorphous to Xꢁrays above 20 GPa, although no clear diffuse scattering signal was detectable
beyond the Compton scattering background produced by the diamond anvils.
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Figure 2. (a) PXRD of C(CN) as a function of pressure up to 20 GPa. Small peaks from the Re gasket
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are visible in some highꢁpressure patterns. The calculated starting pattern is shown below. (b) Unit cell
volume for the R3c structure with pressure. Solid line is the fitted EoS.
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The isolated tetracyanomethane molecule has 21 fundamental vibrational modes. As a crystalline
solid in the R3c structure, the irreproducible representation of all zoneꢁcenter modes is given as
M = 9A + 9A + 18E, of which 24 (A , E) optic modes are both Raman and IR active. For
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comparison purposes, we report mode numbers following fundamental assignments for the
isolated molecule, i.e., 2A (R) + 2E(R) + F (silent) + 4F (IR,R), however, some of these
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fundamentals were observed to split in the solid due to crystalꢁfield effects. Table 1 shows
frequencies of observed Raman and IR modes compared with previous results from the literature.
Table 1. Experimental Raman and IR modes observed for Tetracyanomethane at ~0.1 GPa
ꢁ1
Raman (R)
Infrared (IR)
Experimental observations (cm )
Vibrational mode
Character
(†
■
◊
Solid, solution, vapor)
This study
2285
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†,41
ν (A )
νs (N≡C)
R
2288,
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1
†
,41
ν (A )
νs (CꢁC)
δ (CꢁCꢁN)
δ (CꢁCꢁC)
R
R
R
561, 562, 563
562,
2
1
†
,41
ν3 (E)
ν4 (E)
572
117
573
†,41
115,
ꢀ
,42
ν (F )
δ (CꢁCꢁC)
N/A
ꢁ
136
5
1
R
IR
2281
2281
ꢁ
ν (F )
νas (N≡C)
†,41
◊,41
◊,41
6
2
2276, 2270
†,41
R
IR
1059, 1063
1058,1062
1056 , 1061
ν (F )
νas (CꢁC)
†,41
7
2
1056
R
IR
ꢁ
ꢁ
ꢁ■,42
540
ν (F )
δ (CꢁCꢁN)
δ (CꢁCꢁN)
8
2
R
IR
ꢁ
ꢁ
ꢁ■,42
478
ν (F )
9
2
†,41
νL
νL
νL
νL
Lattice
Lattice
Lattice
Lattice
R
R
R
192
176
156
43
190
†
†
,41
,41
178
154
ꢁ
R
ꢀ
26
Calculated from normal coordinate analysis.
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At our starting pressure of ~0.1 GPa, the observed Raman and IR modes are in general
4
1ꢁ42
agreement with the previous studies.
From a molecular perspective, we follow the mode
4
2
numbering scheme of Gardiner et al. in which the ν (F ) CꢁCꢁC deformation is silent, whereas
5
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Hester et al. assigned ν to the C≡N asymmetric stretch (ν here). We observed that the Raman
5
6
ꢁ1
active CꢁC symmetric stretch (ν ) split into three peaks at 561, 562, 563 cm , whereas Hester et
2
41
ꢁ1
al. only reported a very weak peak at 560 cm . Similarly, we resolved two peaks for CꢁC
ꢁ1
ꢁ1
asymmetric stretching (ν ) at 1059 and 1063 cm in the Raman and at 1058 and 1062 cm in the
7
ꢁ1
41
IR, whereas a single broad peak located at 1056 cm (IR+R) was reported previously. We did
4
2
not observe ν and ν , but Gardiner et al. reported their positions from solution (acetonitrile) IR
8
9
ꢁ1
ꢁ1
measurements at 540 cm and 478 cm , respectively. We observed four Raman lattice modes at
ꢁ1
41
1
92, 176, 156 and 43 cm . Hester et al. reported the same three higherꢁfrequency lattice
ꢁ1
modes, as well as an additional feeble mode at 75 cm . Some differences in frequency are
naturally expected based upon differences in measurement pressure, i.e., 1 bar vs. 1000 bar, but
the crystal structure reamains unchanged.
The pressure dependence of Raman and IR modes is plotted in Figure 3. All modes show an
overall trend of increasing frequency with pressure. No abrupt discontinuities in frequency were
observed with increasing pressure, although frequencies of individual modes do exhibit different
pressure dependencies, and thus different mode Grüneisen parameters. These observations
indicate that C(CN) remains in the starting R3m structure and are in agreement with our PXRD
4
results. Above ~12 GPa the observed intensities of the fundamental Raman and IR modes
decrease significantly, and above 14 GPa none of the original peaks are detectable. New broad
ꢁ1
IR features at ~1335 and ~1600 cm appear above 14 GPa.
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(
a)
(b)
νL ν4 νL
ν2,ν3
ν7
ν6,ν1
ν7
1
3.8 GPa
1
6.1
12.9
1
4.8
10.9
9.8
8.7
7.2
1
1.8
8.5
6.8
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0
5.5
2
.0
.9
3
.0
0
1.0
×
0.75
0.3
×0.75
15
10
5
0
-
1
Frequency (cm )
Figure 3. (a) Raman spectra of C(CN) with pressure. The pressure dependence of individual peaks is
4
shown on the same scale below the spectra. (b) IR absorbance spectra of the ν modes plotted with
7
pressure. Oscillations are interference fringes between the two parallel diamond surfaces. Increasing
ꢁ1
absorbance above ~1500 cm is from the diamond anvils. New broad features marked by arrows at ~1335
ꢁ
1
and ~1600 cm are clearly observed above 14 GPa. The pressure dependence of the peaks is shown in the
panel below the spectra.
In addition to the loss of Raman scattering and IR absorbance of fundamental modes above 12
GPa, new vibrational modes were observed above this pressure, as well as dramatic color
changes of the sample (Figure 4a). No color change was observed in the material between 0 GPa
to 11 GPa, but beyond this pressure the material begins to darken, eventually transforming to a
completely opaque material above ~15 GPa. The loss of fundamental vibrational modes,
combined with drastic color changes and Xꢁray amorphization point to a polymerization reaction
and loss of molecular character. This chemical transformation was observed directly using in situ
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Raman and IR spectroscopy. When the broadꢁrange Raman spectrum is plotted, new broad peaks
ꢁ1
are observed near ~670 and 1400 cm that grow in intensity above ~7 GPa while all other modes
decrease in intensity (Figure 4b). Beyond 14 GPa, only these broad features are observed in the
ꢁ1
ꢁ1
0
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Raman, as well as modes at ~1335 and ~1600 cm in the IR. The Raman feature near 1400 cm
can be deconvolulted into D and G peaks, which are normally observed in amorphous carbon
2
materials and indicate the reaction of the nitrile groups and the formation of new sp C=N / C=C
ꢁ1
bonds. The G and D peak positions at 1323 and 1567 cm , respectively, are consistent with
43ꢁ44
other reports of amorphous carbon nitrides.
The presence of the D peak is an indication that
4
4
ꢁ1
ringꢁlike structures are present. We attribute the broad band near 670 cm to ring rotation
modes, consistent with the polymerization reaction and change in bond order. The presence of
44
ring rotation modes was previously associated with sixꢁmembered ring systems. At ambient
ꢁ1
pressure, this ring rotation “L” mode is centered at 700 cm . Interestingly, this mode shows
frequency softening behavior with increasing pressure.
Figure 4. (aꢁd) In situ optical images of C(CN) collected at several pressures and recovered to 1 atm
4
showing clear visual changes. (e) Broadꢁrange Raman spectra of C(CN) with pressures up to 21 GPa and
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ꢁ
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the recovered sample at 1 atm. New broad features appear above 7 GPa near 670 and 1400 cm .
ꢁ1
Contributions from the diamond anvils near 1350 cm were removed for clarity. Secondꢁorder scattering
ꢁ1
from the anvils is observed near 2500 cm . Raman bands from the recovered sample are centered at 700,
ꢁ1
1290 and 1530 cm .
1
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After achieving a pressure >20 GPa and observing the complete disappearance of nitrile Raman
modes, diamond anvil cell samples were decompressed to ambient conditions for subsequent
analysis of the reaction product. The microsctructure and chemical composition were examined
using SEM with EDS as shown in Figure 5. SEM/EDS analysis reveals that samples have a
smooth, uniform texture with an average chemical composition of 59.8 at% C, 40.0 at% N and
0
.2 at% O. The observed composition of C N is somewhat nitrogen deficient compared with
5 3.34
the starting molecule (C N ), but the result indicates that no significant chemical
5
4
disproportionation occurs during the transformation and that the new material is recoverable to
ambient conditions and stable in air. We note that EDS analysis typically biases carbon due to
column contamination (many samples are carbon coated) and other organic sources. The small
amount of oxygen observed is likely due to slight surface oxidation as all sample loadings were
conducted in an inert Ar atmosphere.
HRTEM measurements conducted on the crushed sample after it was removed from the gasket
show that the material is disordered on the nanometer scale and no longꢁrange correlations are
observed in the fast Fourier transform (FFT) image. We note that the sample is sensitive to
electron beam exposure and significant graphitization was observed after exposing the sample to
the 200 kV electron beam on the time scale of minutes. This fact prevented further quantitative
characterization using electron energy loss spectroscopy.
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Figure 5. (A) SEM image of recovered sample in Re gasket. (B) EDS compositional maps for carbon
(
red) and nitrogen (blue) showing uniform chemical composition. (C) HRTEM image of recovered
sample showing disorder on the atomic scale. The inset displays the FFT.
Based upon PXRD, Raman, IR and SEM/TEM analyses, it is clear that tetracyanomethane
undergoes an irreversible polymerization process, beginning above ca. 7 GPa, and that it is
indeed possible to form extended network solids through the polymerization of precursor
3
molecules with sp carbon centers. The polymerization product is recoverable to ambient
2
conditions and consists of predominantly sp bonds in ringꢁlike motifs with a bulk composition
similar to the starting material, as verified by Raman and EDS measurements. One plausible
product of the polymerization process is the formation of distorted 1,3,5ꢁtriazine rings that would
form through trimerization of three cyanide groups, each contributed by three neighboring
tetracyanomethane molecules. These rings would then be linked together by the starting central
3
3
sp carbon atom, leading to an extended network solid. It is possible for each central sp carbon
atom to be bonded with up to four triazine rings within the idealized structure. Within the actual
material, it is likely that tetracyanomethane molecules react to form multiꢁmembered rings
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exhibiting a variety of local environments. Due to the fact that many competitive reaction
pathways are possible, the resulting material does not exhibit any longꢁrange order. Given that
the process proceeds at room temperature, it seems unlikely that any bonding changes would
3
1
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occur for the central sp starting carbon and all chemistry proceeds through the reactive nitrile
groups. Larger volume scaling of the reaction product would allow for a sufficient amount of
sample to be characterized by other techniques such as NMR.
CONCLUSION
The chemical and structural changes of tetracyanomethane were examined for the first time
under highꢁpressure conditions using Raman and IR spectroscopy and synchrotron Xꢁray
diffraction. The results indicate that extended solid networks can be constructed from precursor
3
molecules with builtꢁin sp functionality. C(CN) begins to polymerize above ~7 GPa at room
4
temperature and the process is completed by ~20 GPa during compression on the time scale of
hours. The polymerization product possesses a similar bulk composition to the starting material,
is recoverable to ambient conditions and is unreactive in air. These results suggest the possibility
for targeted pressureꢁinduced polymerization with premeditated functionality designed into the
precursor molecule.
AUTHOR INFORMATION
Corresponding Authors
*
D. W. Keefer. Eꢁmail: keefer.derek@gmail.com. Telephone: 814ꢁ863ꢁ0556.
*T. A. Strobel. Eꢁmail: tstrobel@ciw.edu. Telephone: 202ꢁ478ꢁ8943.
Notes
The authors declare no competing financial interest.
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ACKNOWLEDGEMENTS
We thank R. Hrubiak for assistance with XRD measurements. This work was supported by
DARPA under ARO Contract No. 31P4Qꢁ13ꢁ1ꢁ0005. Portions of this work were performed at
HPCAT (Sector 16), Advanced Photon Source (APS), Argonne National Laboratory. HPCAT
operations are supported by DOEꢁNNSA under Award No. DEꢁNA0001974, with partial
instrumentation funding by NSF. The Advanced Photon Source is a U.S. Department of Energy
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(DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne
National Laboratory under Contract No. DEꢁAC02ꢁ06CH11357.
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