Impact of Architectural Asymmetry on Frank-Kasper Phase Formation in Block Polymer Melts
Abstract not provided
Chang, Alice B.↗
SEARCH · Search NASA
Results for “Frank-Kasper phases”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Solvent Isotherms and Structural Transitions in Nanoparticle Superlattice Assembly
Here, we introduce a Molecular Theory for Compressible Fluids (MOLT-CF) that enables us to compute free energies and other thermodynamic functions for nanoparticle superlattices with any solvent content, including the dry limit. Quantitative agreement is observed between MOLT-CF and united-atom molecular dynamics simulations performed to assess the reliability and precision of the theory. Among other predictions, MOLT-CF shows that the amount of solvent within the superlattice decreases approximately linearly with its vapor pressure and that in the late stages of drying, solvent-filled voids form at lattice interstitials. Applied to single-component superlattices, MOLT-CF predicts fcc-to-bcc Bain transitions for decreasing vapor pressure and for increasing ligand length, both in agreement with experimental results. We explore the stability of other single-component phases and show that the C14 Frank-Kasper phase, which has been reported in experiments, is not a global free-energy minimum. Implications for precise assembly and prediction of multicomponent nanoparticle systems are discussed.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
An Exceptionally Stable and Scalable Sugar-Polyolefin Frank-Kasper A15 Phase
Explore the source record for details and available documents.
99 GENERAL AND MISCELLANEOUS↗
Towards libraries of different ultrasmall amorphous silica cage topologies
Cage topology controlled at the nanometer length scale is expected to enable original functionalities, e.g., in catalysis and therapeutics. Cages are fundamental structural motifs of clathrates and their topological duals, Frank-Kasper phases, and are constituents of mesoporous silica frameworks. However, with one exception, they have not been synthesized as discrete particles. By varying reactant ratios of surfactant, oil, and silane, we report the discovery of 5(12)6(2) and 5(12)6(8) amorphous silica polyhedra, each coexisting with the previously identified 5(12) cage, using combined cryo-transmission electron microscopy (cryo-TEM) and single-particle reconstruction (SPR). Notably, the 5(12)6(8) polyhedron represents a topology not previously observed in mesoporous silica frameworks. Control over structural features is demonstrated, and insights into cage formation mechanisms are provided. Structural outcomes are summarized in a ternary morphology diagram alongside prior results, bridging serendipitous discovery and intentional design of silica cages displaying a level of control over silica polymerization rivaling nature.
Jang, Dong June [Department of Materials Science a↗
Self-assembled complex micelle phase stability in ABA-type triblock copolymers and related core-shell bottlebrushes
We report the synthesis and temperature-dependent morphologies of a series of polylactide--poly (-decalactone)--polylactide (LDL) triblock copolymers with M n = 16.0 – 18.1 kg / mol and volume fractions f L = 0.27 – 0.31 and associated core-shell bottlebrush (csBB) polymers, which derive from enchaining LDL triblocks through a polymerizable midchain functionality. While the LDL triblocks form micellar Frank-Kasper A15 and phases due to the conformational asymmetry of this monomer pair, the csBB morphologies sensitively depend on the backbone degree of polymerization ( N bb ). At low N bb values, micellar Frank-Kasper phases with the brush backbone situated in the matrix domain are stable, albeit with a modest reduction in the mean interfacial curvature evidenced by a to A15 order-to-order transition. However, larger N bb values drive csBBs to form hexagonally packed cylinders phases. This N bb -dependent phase behavior is rationalized in terms of a star-to-bottlebrush transition. At low N bb values, the csBBs are akin to star polymers with pointlike junctions that can support complex micelle packings. As N bb increases, the csBBs adopt cylindrical molecular geometries with extended backbones situated in the matrix domain that prefer hexagonally packed cylinders morphologies. Published by the American Physical Society 2024
Materials Science↗
Modifying Frank–Kasper Mesophases by Modulating Chain Configuration in PDMS- b -PTFEA Copolymers
The common spherical mesophases observed from chemically distinct compounds have promoted extensive studies of packing structures in soft-matter self-assemblies. In this report we present a new approach for controlling sphere-packing phases by modulating homologous copolymer chain configurations. To this end, three sets of sample pairs, compositionally asymmetric polydimethylsiloxane-b-poly(2,2,2-trifluoroethyl acrylate) (PDMS-b-PTFEA) diblock copolymers (diBCPs) and their homologues containing the corresponding triblock copolymer (triBCP), are synthesized via atom transfer radical polymerization and designed with the consistent volume fractions of the core-forming PTFEA block, f PTFEA = 0.20, 0.18, and 0.15. We identify the formation of C15 and hexagonally close-packed (HCP) phases in the triBCP-containing PDMS-b-PTFEAs, whereas the sigma and C14 phases are formed in their diBCP analogues, respectively. These phase shifts into C15 and HCP, due to molecular configuration differences, reveal a significant yet unrealized role of chain configurations and the associated chain size effects in determining the stable sphere-packing phases in BCP systems.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Various Low-Symmetry Phases in High- χ and Conformationally Asymmetric PDMS- b -PTFEA Copolymers
Since the discovery of the Frank–Kasper (FK) phase a decade ago, single-component block copolymer systems have offered unique opportunities to explore the structural and phase-transition properties of topologically close-packed FK phases composed of point-particle motifs. Here, we present the formation of complex low-symmetry phases and their thermodynamic stability using high-χ and high-ε linear diblock copolymers, where χ and ε are the Flory–Huggins interaction parameter and conformational asymmetry between the two blocks, respectively. In this work, a series of polydimethylsiloxane-b-poly(2,2,2-trifluoroethyl acrylate) (PDMS-b-PTFEA) copolymers are prepared by tuning the volume fraction ($f_{\text{PTFEA}}$) of a minor PTFEA block. The packing structures of PDMS-b-PTFEAs are mapped in the space of temperature versus $f_{\text{PTFEA}}$ using X-ray scattering measurements. In addition to the packing structures reported earlier, we identify another A15 phase at higher $f_{\text{PTFEA}}$ close to a hexagonally packed cylinder (HEX) phase and establish the phase sequence of HEX–A15–σ–C14–BCC with decreasing $f_{\text{PTFEA}}$. Theoretical calculation of relative free-energy densities confirms the experimental phase sequence of the composition-dependent sphere-packing structures. Interestingly, the domain sizes of three-dimensional (3D) sphere-packing structures are nearly temperature-invariant compared to that of a two-dimensional HEX structure, and we attribute this dimensional stability to the strong enthalpic effects in the formation of 3D packing structures and the geometrical characteristics of spherical domains. Our results demonstrate that the interaction parameter χ, together with the known role of conformational asymmetry ε, serves as the primary thermodynamic parameter for selecting and stabilizing various low-symmetry packing structures in sphere-forming linear diblock copolymer systems.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Mesoscale Frank–Kasper Crystal Structures from Dendron Assembly by Controlling Core Apex Interactions
Single-component polymeric materials open up a great potential for self-assembly into mesoscale complex crystal structures that are known as Frank-Kasper (FK) phases. Predicting the packing structures of the soft-matter spheres, however, remains a challenge even when the molecular design is precisely known. Here, we investigate the role of the molecules' enthalpic interaction in determining the low-symmetry crystal structures. To this end, we synthesize architecturally asymmetric dendrons by varying their apex functionalities and examine the packing structures of the second-generation (G2) dendritic wedges. Our work shows that weakening the hydrogen bonding of the dendron apex makes the particles softer and smaller, and leads to the formation of various FK structures at lower temperatures, including the new observation of a FK C14 phase in the cone-shaped dendron systems. As a consequence of the free energy balance between the particle's interfacial tension and the chain's stretching, various packing structures are mainly tuned by designing the hydrogen bonding interaction.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Particle Dynamics in a Diblock-Copolymer-Based Dodecagonal Quasicrystal and Its Periodic Approximant by X-Ray Photon Correlation Spectroscopy
Temperature-dependent X-ray photon correlation spectroscopy (XPCS) measurements are reported for a binary diblock copolymer blend that self-assembles into an aperiodic dodecagonal quasicrystal (DDQC) and a periodic Frank-Kasper σ phase approximant. The measured structural relaxation times are Bragg scattering wavevector-independent and are five times faster in the DDQC than the σ phase, with minimal temperature dependence. Further, the underlying dynamical relaxations are ascribed to differences in particle motion at the grain boundaries within each of these tetrahedrally close-packed assemblies. These results identify unprecedented particle dynamics measurements of tetrahedrally-coordinated micellar block polymers, thus expanding the application of XPCS to ordered soft materials.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Materials Data on Fe7Mo6 by Materials Project
Fe7Mo6 is Frank-Kasper $\mu$ Phase structured and crystallizes in the trigonal R-3m space group. The structure is three-dimensional. there are three inequivalent Mo sites. In the first Mo site, Mo is bonded in a 6-coordinate geometry to four Mo and twelve Fe atoms. There are one shorter (2.66 Å) and three longer (2.83 Å) Mo–Mo bond lengths. There are a spread of Mo–Fe bond distances ranging from 2.66–2.87 Å. In the second Mo site, Mo is bonded in a 6-coordinate geometry to nine Mo and six equivalent Fe atoms. There are a spread of Mo–Mo bond distances ranging from 2.75–3.03 Å. There are three shorter (2.68 Å) and three longer (2.71 Å) Mo–Fe bond lengths. In the third Mo site, Mo is bonded in a 8-coordinate geometry to eight Mo and six equivalent Fe atoms. The Mo–Mo bond length is 2.52 Å. All Mo–Fe bond lengths are 2.60 Å. There are two inequivalent Fe sites. In the first Fe site, Fe is bonded to seven Mo and five Fe atoms to form a mixture of edge, face, and corner-sharing FeFe5Mo7 cuboctahedra. There are a spread of Fe–Fe bond distances ranging from 2.37–2.39 Å. In the second Fe site, Fe is bonded to six equivalent Mo and six equivalent Fe atoms to form FeFe6Mo6 cuboctahedra that share corners with twelve equivalent FeFe5Mo7 cuboctahedra, edges with six equivalent FeFe6Mo6 cuboctahedra, and faces with eighteen equivalent FeFe5Mo7 cuboctahedra.
36 MATERIALS SCIENCE↗
Materials Data on Nb6Co7 by Materials Project
Co7Nb6 is Frank-Kasper $\mu$ Phase structured and crystallizes in the trigonal R-3m space group. The structure is three-dimensional. there are three inequivalent Nb sites. In the first Nb site, Nb is bonded in a 6-coordinate geometry to nine Nb and six equivalent Co atoms. There are a spread of Nb–Nb bond distances ranging from 2.83–3.14 Å. There are three shorter (2.73 Å) and three longer (2.80 Å) Nb–Co bond lengths. In the second Nb site, Nb is bonded in a 6-coordinate geometry to four Nb and twelve Co atoms. There are one shorter (2.75 Å) and three longer (2.88 Å) Nb–Nb bond lengths. There are a spread of Nb–Co bond distances ranging from 2.67–2.99 Å. In the third Nb site, Nb is bonded in a 8-coordinate geometry to eight Nb and six equivalent Co atoms. The Nb–Nb bond length is 2.68 Å. All Nb–Co bond lengths are 2.66 Å. There are two inequivalent Co sites. In the first Co site, Co is bonded to six equivalent Nb and six equivalent Co atoms to form CoNb6Co6 cuboctahedra that share corners with twelve equivalent CoNb7Co5 cuboctahedra, edges with six equivalent CoNb6Co6 cuboctahedra, and faces with eighteen equivalent CoNb7Co5 cuboctahedra. All Co–Co bond lengths are 2.43 Å. In the second Co site, Co is bonded to seven Nb and five Co atoms to form CoNb7Co5 cuboctahedra that share corners with fifteen CoNb6Co6 cuboctahedra, edges with five equivalent CoNb7Co5 cuboctahedra, and faces with thirteen CoNb6Co6 cuboctahedra. There are two shorter (2.43 Å) and two longer (2.47 Å) Co–Co bond lengths.
36 MATERIALS SCIENCE↗
Materials Data on Ca3Al7Ag2 by Materials Project
Ca3Ag2Al7 is Frank-Kasper $\mu$ Phase-derived structured and crystallizes in the trigonal R-3m space group. The structure is three-dimensional. there are two inequivalent Ca sites. In the first Ca site, Ca is bonded in a distorted hexagonal planar geometry to six equivalent Ag and twelve equivalent Al atoms. All Ca–Ag bond lengths are 3.26 Å. All Ca–Al bond lengths are 3.59 Å. In the second Ca site, Ca is bonded in a 12-coordinate geometry to twelve Al atoms. There are a spread of Ca–Al bond distances ranging from 3.26–3.31 Å. Ag is bonded in a 9-coordinate geometry to three equivalent Ca and six equivalent Al atoms. There are three shorter (2.72 Å) and three longer (2.78 Å) Ag–Al bond lengths. There are two inequivalent Al sites. In the first Al site, Al is bonded in a 12-coordinate geometry to five Ca, two equivalent Ag, and five Al atoms. There are a spread of Al–Al bond distances ranging from 2.77–2.87 Å. In the second Al site, Al is bonded to six equivalent Ca and six equivalent Al atoms to form edge-sharing AlCa6Al6 cuboctahedra.
36 MATERIALS SCIENCE↗
Materials Data on Mg2SiNi3 by Materials Project
Mg2Ni3Si is Frank-Kasper $\mu$ Phase-derived structured and crystallizes in the trigonal R-3m space group. The structure is three-dimensional. Mg is bonded in a 12-coordinate geometry to four equivalent Mg, nine equivalent Ni, and three equivalent Si atoms. There are one shorter (2.76 Å) and three longer (3.03 Å) Mg–Mg bond lengths. There are three shorter (2.71 Å) and six longer (2.86 Å) Mg–Ni bond lengths. All Mg–Si bond lengths are 2.92 Å. Ni is bonded to six equivalent Mg, four equivalent Ni, and two equivalent Si atoms to form NiMg6Si2Ni4 cuboctahedra that share corners with four equivalent SiMg6Ni6 cuboctahedra, corners with fourteen equivalent NiMg6Si2Ni4 cuboctahedra, edges with six equivalent NiMg6Si2Ni4 cuboctahedra, faces with six equivalent SiMg6Ni6 cuboctahedra, and faces with twelve equivalent NiMg6Si2Ni4 cuboctahedra. All Ni–Ni bond lengths are 2.50 Å. Both Ni–Si bond lengths are 2.33 Å. Si is bonded to six equivalent Mg and six equivalent Ni atoms to form SiMg6Ni6 cuboctahedra that share corners with six equivalent SiMg6Ni6 cuboctahedra, corners with twelve equivalent NiMg6Si2Ni4 cuboctahedra, edges with six equivalent SiMg6Ni6 cuboctahedra, and faces with eighteen equivalent NiMg6Si2Ni4 cuboctahedra.
36 MATERIALS SCIENCE↗
Materials Data on Th6Cd7 by Materials Project
Th6Cd7 is Frank-Kasper $\mu$ Phase-like structured and crystallizes in the orthorhombic Pbam space group. The structure is three-dimensional. there are three inequivalent Th sites. In the first Th site, Th is bonded in a 9-coordinate geometry to seven Th and eight Cd atoms. There are a spread of Th–Th bond distances ranging from 3.27–3.78 Å. There are a spread of Th–Cd bond distances ranging from 3.42–3.58 Å. In the second Th site, Th is bonded in a 10-coordinate geometry to six Th and ten Cd atoms. There are a spread of Th–Th bond distances ranging from 3.56–3.90 Å. There are a spread of Th–Cd bond distances ranging from 3.45–3.70 Å. In the third Th site, Th is bonded in a 7-coordinate geometry to eight Th and six Cd atoms. The Th–Th bond length is 3.11 Å. There are a spread of Th–Cd bond distances ranging from 3.35–3.39 Å. There are three inequivalent Cd sites. In the first Cd site, Cd is bonded to six Th and six Cd atoms to form CdTh6Cd6 cuboctahedra that share corners with ten CdTh7Cd5 cuboctahedra, edges with two equivalent CdTh6Cd6 cuboctahedra, and faces with sixteen CdTh7Cd5 cuboctahedra. There are four shorter (3.04 Å) and two longer (3.05 Å) Cd–Cd bond lengths. In the second Cd site, Cd is bonded to seven Th and five Cd atoms to form CdTh7Cd5 cuboctahedra that share corners with twelve CdTh6Cd6 cuboctahedra, edges with three equivalent CdTh7Cd5 cuboctahedra, and faces with fourteen CdTh6Cd6 cuboctahedra. There are two shorter (3.03 Å) and two longer (3.04 Å) Cd–Cd bond lengths. In the third Cd site, Cd is bonded to seven Th and five Cd atoms to form CdTh7Cd5 cuboctahedra that share corners with thirteen CdTh6Cd6 cuboctahedra, edges with five equivalent CdTh7Cd5 cuboctahedra, and faces with thirteen CdTh6Cd6 cuboctahedra. There are one shorter (2.95 Å) and one longer (3.09 Å) Cd–Cd bond lengths.
36 MATERIALS SCIENCE↗
Materials Data on URe2 by Materials Project
URe2 is Frank-Kasper $\mu$ Phase-like structured and crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. U is bonded in a 8-coordinate geometry to two equivalent U and twelve Re atoms. There are one shorter (2.77 Å) and one longer (3.19 Å) U–U bond lengths. There are a spread of U–Re bond distances ranging from 2.99–3.35 Å. There are three inequivalent Re sites. In the first Re site, Re is bonded to six equivalent U and six Re atoms to form a mixture of edge, corner, and face-sharing ReU6Re6 cuboctahedra. There are two shorter (2.60 Å) and four longer (2.67 Å) Re–Re bond lengths. In the second Re site, Re is bonded to six equivalent U and six Re atoms to form a mixture of edge, corner, and face-sharing ReU6Re6 cuboctahedra. There are two shorter (2.57 Å) and two longer (2.78 Å) Re–Re bond lengths. In the third Re site, Re is bonded to six equivalent U and six Re atoms to form a mixture of distorted edge, corner, and face-sharing ReU6Re6 cuboctahedra. There are one shorter (2.90 Å) and one longer (2.98 Å) Re–Re bond lengths.
36 MATERIALS SCIENCE↗
Materials Data on Gd3Al7Ag2 by Materials Project
Gd3Ag2Al7 is Frank-Kasper $\mu$ Phase-derived structured and crystallizes in the trigonal R-3m space group. The structure is three-dimensional. there are two inequivalent Gd sites. In the first Gd site, Gd is bonded in a 12-coordinate geometry to twelve Al atoms. There are a spread of Gd–Al bond distances ranging from 3.19–3.29 Å. In the second Gd site, Gd is bonded in a distorted hexagonal planar geometry to six equivalent Ag and twelve equivalent Al atoms. All Gd–Ag bond lengths are 3.22 Å. All Gd–Al bond lengths are 3.56 Å. Ag is bonded in a 9-coordinate geometry to three equivalent Gd and six equivalent Al atoms. There are three shorter (2.71 Å) and three longer (2.78 Å) Ag–Al bond lengths. There are two inequivalent Al sites. In the first Al site, Al is bonded in a 12-coordinate geometry to five Gd, two equivalent Ag, and five Al atoms. There are three shorter (2.74 Å) and two longer (2.84 Å) Al–Al bond lengths. In the second Al site, Al is bonded to six equivalent Gd and six equivalent Al atoms to form edge-sharing AlGd6Al6 cuboctahedra.
36 MATERIALS SCIENCE↗
Materials Data on DySiNi4 by Materials Project
DyNi4Si is Frank-Kasper $\mu$ Phase-derived structured and crystallizes in the orthorhombic Cmmm space group. The structure is three-dimensional. Dy is bonded in a 6-coordinate geometry to fourteen Ni and four equivalent Si atoms. There are a spread of Dy–Ni bond distances ranging from 2.80–3.11 Å. All Dy–Si bond lengths are 3.21 Å. There are two inequivalent Ni sites. In the first Ni site, Ni is bonded in a 12-coordinate geometry to three equivalent Dy, five Ni, and two equivalent Si atoms. There are four shorter (2.46 Å) and one longer (2.57 Å) Ni–Ni bond lengths. Both Ni–Si bond lengths are 2.35 Å. In the second Ni site, Ni is bonded to four equivalent Dy, six Ni, and two equivalent Si atoms to form NiDy4Si2Ni6 cuboctahedra that share corners with four equivalent SiDy4Ni8 cuboctahedra, corners with twelve equivalent NiDy4Si2Ni6 cuboctahedra, edges with four equivalent SiDy4Ni8 cuboctahedra, edges with six equivalent NiDy4Si2Ni6 cuboctahedra, faces with four equivalent SiDy4Ni8 cuboctahedra, and faces with six equivalent NiDy4Si2Ni6 cuboctahedra. Both Ni–Ni bond lengths are 2.54 Å. Both Ni–Si bond lengths are 2.41 Å. Si is bonded to four equivalent Dy and eight Ni atoms to form distorted SiDy4Ni8 cuboctahedra that share corners with eight equivalent NiDy4Si2Ni6 cuboctahedra, corners with eight equivalent SiDy4Ni8 cuboctahedra, edges with two equivalent SiDy4Ni8 cuboctahedra, edges with eight equivalent NiDy4Si2Ni6 cuboctahedra, faces with two equivalent SiDy4Ni8 cuboctahedra, and faces with eight equivalent NiDy4Si2Ni6 cuboctahedra.
36 MATERIALS SCIENCE↗
Materials Data on CeZnNi2 by Materials Project
CeNi2Zn is Frank-Kasper $\mu$ Phase-derived structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are four inequivalent Ce sites. In the first Ce site, Ce is bonded in a 12-coordinate geometry to one Ce, nine equivalent Ni, and three equivalent Zn atoms. The Ce–Ce bond length is 3.34 Å. There are six shorter (2.94 Å) and three longer (3.17 Å) Ce–Ni bond lengths. All Ce–Zn bond lengths are 3.13 Å. In the second Ce site, Ce is bonded in a 12-coordinate geometry to one Ce, nine equivalent Ni, and three equivalent Zn atoms. The Ce–Ce bond length is 3.34 Å. There are six shorter (2.94 Å) and three longer (3.17 Å) Ce–Ni bond lengths. All Ce–Zn bond lengths are 3.13 Å. In the third Ce site, Ce is bonded in a 12-coordinate geometry to one Ce, nine equivalent Ni, and three equivalent Zn atoms. The Ce–Ce bond length is 3.34 Å. There are six shorter (2.94 Å) and three longer (3.17 Å) Ce–Ni bond lengths. All Ce–Zn bond lengths are 3.13 Å. In the fourth Ce site, Ce is bonded in a 6-coordinate geometry to two Ce, twelve equivalent Ni, and six Zn atoms. All Ce–Ni bond lengths are 3.33 Å. All Ce–Zn bond lengths are 3.04 Å. Ni is bonded to five Ce, four equivalent Ni, and three Zn atoms to form distorted NiCe5Zn3Ni4 cuboctahedra that share corners with two equivalent ZnCe6Ni6 cuboctahedra, corners with fifteen equivalent NiCe5Zn3Ni4 cuboctahedra, edges with eight equivalent NiCe5Zn3Ni4 cuboctahedra, faces with three equivalent ZnCe6Ni6 cuboctahedra, and faces with eleven equivalent NiCe5Zn3Ni4 cuboctahedra. There are two shorter (2.61 Å) and two longer (2.66 Å) Ni–Ni bond lengths. There are a spread of Ni–Zn bond distances ranging from 2.53–2.56 Å. There are three inequivalent Zn sites. In the first Zn site, Zn is bonded in a 9-coordinate geometry to three equivalent Ce and six equivalent Ni atoms. In the second Zn site, Zn is bonded in a 9-coordinate geometry to three equivalent Ce and six equivalent Ni atoms. In the third Zn site, Zn is bonded to six Ce and six equivalent Ni atoms to form ZnCe6Ni6 cuboctahedra that share corners with twelve equivalent NiCe5Zn3Ni4 cuboctahedra, edges with six equivalent ZnCe6Ni6 cuboctahedra, and faces with eighteen equivalent NiCe5Zn3Ni4 cuboctahedra.
36 MATERIALS SCIENCE↗