Energy vs. Entropy in Superlattices of Ligand-Covered Nanoparticles

2019 ◽  
Author(s):  
Zhaochuan Fan ◽  
Michael Gruenwald
Keyword(s):  
Potential Energy ◽  
Driving Forces ◽  
Molecular Model ◽  
Configurational Entropy ◽  
Nearest Neighbors ◽  
Coarse Grained ◽  
Face Centered Cubic ◽  
Body Centered Cubic ◽  
Core Size ◽  
Face Centered

Nanoparticles covered with short ligands tend to self-assemble into face-centered cubic (fcc) superlattices, while nanoparticles with longer ligands preferentially form body-centered cubic (bcc) superlattices. The thermodynamic driving forces for these structures are not fully understood and conflicting theories have been proposed. In this paper, we systematically study the thermodynamic stability of fcc and bcc superlattices as a function of ligand length, core size, and ligand coverage with a coarse-grained molecular model. Our simulations reveal that bcc superlattices are stabilized via two fundamentally different mechanisms, depending on ligand length. For shorter ligands, the bcc superlattice has a lower potential energy than fcc, due to additional interactions between ligands on next-nearest neighbors in the superlattice. For longer ligands, the bcc superlattice is stabilized due to a larger configurational entropy of ligands.

Energy vs. Entropy in Superlattices of Ligand-Covered Nanoparticles

2019 ◽  
Author(s):  
Zhaochuan Fan ◽  
Michael Gruenwald
Keyword(s):  
Potential Energy ◽  
Driving Forces ◽  
Molecular Model ◽  
Configurational Entropy ◽  
Nearest Neighbors ◽  
Coarse Grained ◽  
Face Centered Cubic ◽  
Body Centered Cubic ◽  
Core Size ◽  
Face Centered

Nanoparticles covered with short ligands tend to self-assemble into face-centered cubic (fcc) superlattices, while nanoparticles with longer ligands preferentially form body-centered cubic (bcc) superlattices. The thermodynamic driving forces for these structures are not fully understood and conflicting theories have been proposed. In this paper, we systematically study the thermodynamic stability of fcc and bcc superlattices as a function of ligand length, core size, and ligand coverage with a coarse-grained molecular model. Our simulations reveal that bcc superlattices are stabilized via two fundamentally different mechanisms, depending on ligand length. For shorter ligands, the bcc superlattice has a lower potential energy than fcc, due to additional interactions between ligands on next-nearest neighbors in the superlattice. For longer ligands, the bcc superlattice is stabilized due to a larger configurational entropy of ligands.

Voids in Irradiated Tungsten and Molybdenum

1969 ◽  
Vol 27 ◽  
pp. 190-191
Author(s):  
Robert C. Rau ◽  
Robert L. Ladd
Keyword(s):  
Melting Point ◽  
Fast Neutron ◽  
Neutron Irradiation ◽  
Elevated Temperatures ◽  
Irradiation Temperature ◽  
The Body ◽  
Face Centered Cubic ◽  
Body Centered Cubic ◽  
Cubic Metals ◽  
Face Centered

Recent studies have shown the presence of voids in several face-centered cubic metals after neutron irradiation at elevated temperatures. These voids were found when the irradiation temperature was above 0.3 Tm where Tm is the absolute melting point, and were ascribed to the agglomeration of lattice vacancies resulting from fast neutron generated displacement cascades. The present paper reports the existence of similar voids in the body-centered cubic metals tungsten and molybdenum.

scholarly journals Irradiation Behaviors in BCC Multi-Component Alloys with Different Lattice Distortions

Metals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 706
Author(s):  
Yue Su ◽  
Songqin Xia ◽  
Jia Huang ◽  
Qingyuan Liu ◽  
Haocheng Liu ◽  
...  
Keyword(s):  
Single Phase ◽  
Vacuum Arc ◽  
Face Centered Cubic ◽  
Body Centered Cubic ◽  
Chemical Complexity ◽  
Arc Melting ◽  
Vacuum Arc Melting ◽  
Lattice Distortions ◽  
Face Centered ◽  
Displacement Per Atom

Recently, the irradiation behaviors of multi-component alloys have stimulated an increasing interest due to their ability to suppress the growth of irradiation defects, though the mostly studied alloys are limited to face centered cubic (fcc) structured multi-component alloys. In this work, two single-phase body centered cubic (bcc) structured multi-component alloys (CrFeV, AlCrFeV) with different lattice distortions were prepared by vacuum arc melting, and the reference of α-Fe was also prepared. After 6 MeV Au ions irradiation to over 100 dpa (displacement per atom) at 500 °C, the bcc structured CrFeV and AlCrFeV exhibited significantly improved irradiation swelling resistance compared to α-Fe, especially AlCrFeV. The AlCrFeV alloy possesses superior swelling resistance, showing no voids compared to α-Fe and CrFeV alloy, and scarce irradiation softening appears in AlCrFeV. Owing to their chemical complexity, it is believed that the multi-component alloys under irradiation have more defect recombination and less damage accumulation. Accordingly, we discuss the origin of irradiation resistance and the Al effect in the studied bcc structured multi-component alloys.

scholarly journals Size-Dependent Alloying Ability of Immiscible W-Cu Bimetallic Nanoparticles: A Theoretical and Experimental Study

Nanomaterials ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 1047
Author(s):  
Hongbo Zhang ◽  
Tao Liu ◽  
Siqi Zhao ◽  
Zhanyuan Xu ◽  
Yaozha Lv ◽  
...  
Keyword(s):  
Binary Systems ◽  
Bimetallic Nanoparticles ◽  
Driving Forces ◽  
Phase Particle ◽  
Phase Segregation ◽  
High Yield ◽  
Universal Method ◽  
Face Centered Cubic ◽  
Original Size ◽  
Face Centered

The preparation of alloyed bimetallic nanoparticles (BNPs) between immiscible elements is always a huge challenge due to the lack of thermodynamic driving forces. W–Cu is a typical immiscible binary system, and it is difficult to alloy them under conventional circumstances. Here, we used the bond energy model (BEM) to calculate the effect of size on the alloying ability of W–Cu systems. The prediction results show that reducing the synthesis size (the original size of W and Cu) to less than 10 nm can obtain alloyed W–Cu BNPs. Moreover, we prepared alloyed W50Cu50 BNPs with a face-centered-cubic (FCC) crystalline structure via the nano in situ composite method. Energy-dispersive X-ray spectroscopy (EDS) coupled with scan transmission electron microscopy (STEM) confirmed that W and Cu are well mixed in a single-phase particle, instead of a phase segregation into a core-shell or other heterostructures. The present results suggest that the nanoscale size effect can overcome the immiscibility in immiscible binary systems. In the meantime, this work provided a high-yield and universal method for preparing alloyed BNPs between immiscible elements.

MINIMAL KNOTTING NUMBERS

2009 ◽  
Vol 18 (08) ◽  
pp. 1159-1173 ◽  
Author(s):  
CASEY MANN ◽  
JENNIFER MCLOUD-MANN ◽  
RAMONA RANALLI ◽  
NATHAN SMITH ◽  
BENJAMIN MCCARTY
Keyword(s):  
The Body ◽  
Computer Algorithm ◽  
Face Centered Cubic ◽  
Body Centered Cubic ◽  
Cubic Lattice ◽  
The Face ◽  
Face Centered ◽  
Body Centered Cubic Lattice

This article concerns the minimal knotting number for several types of lattices, including the face-centered cubic lattice (fcc), two variations of the body-centered cubic lattice (bcc-14 and bcc-8), and simple-hexagonal lattices (sh). We find, through the use of a computer algorithm, that the minimal knotting number in sh is 20, in fcc is 15, in bcc-14 is 13, and bcc-8 is 18.

Poisson's Ratio for Central-Force Polycrystals

1976 ◽  
Vol 31 (12) ◽  
pp. 1539-1542 ◽  
Author(s):  
H. M. Ledbetter
Keyword(s):  
Electron Energy ◽  
Poisson Ratio ◽  
The Body ◽  
Central Force ◽  
Face Centered Cubic ◽  
Polycrystalline Aggregate ◽  
Body Centered Cubic ◽  
The Face ◽  
Predicted Values ◽  
Face Centered

Abstract The Poisson ratio υ of a polycrystalline aggregate was calculated for both the face-centered cubic and the body-centered cubic cases. A general two-body central-force interatomatic potential was used. Deviations of υ from 0.25 were verified. A lower value of υ is predicted for the f.c.c. case than for the b.c.c. case. Observed values of υ for twenty-three cubic elements are discussed in terms of the predicted values. Effects of including volume-dependent electron-energy terms in the inter-atomic potential are discussed.

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