scholarly journals Complex modeling for the quantification of nanoscale disorder using genetic algorithms, density functional theory and line-profile analysis

2020 ◽  
Vol 53 (4) ◽  
pp. 1087-1100
Author(s):  
Robert J. Koch ◽  
Guangfang Li ◽  
Shubham Pandey ◽  
Simon R. Phillpot ◽  
Hui Wang ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Atomic Structure ◽  
Disordered Systems ◽  
Density Functional ◽  
Lattice Strain ◽  
Profile Analysis ◽  
Density Functional Theory Calculations ◽  
Line Profile Analysis ◽  
Optimization Approach ◽  
Functional Theory

A new, computationally efficient, complex modeling approach is presented for the quantification of the local and average atomic structure, nanostructure and microstructure of an Au0.25Cu0.75 alloy. High-resolution X-ray powder diffraction and whole pattern fitting show that the sample is phase pure, with isotropic lattice strain and a distribution of equiaxed crystallites of mean size 144 (11) nm, where each crystallite has on average four twin boundaries and an average of three deformation faults per four crystallites. Both small- and large-box model optimizations were used to extract local and long-range information from the pair distribution function. The large-box, 640 000-atom-ensemble optimization approach applied herein relies on differential evolution optimization and shows that the alloy has chemical short-range ordering, with correlation parameters of −0.26 (2) and 0.36 (8) in the first and second correlation shells, respectively. Locally, there is a 1.45 (8)% tetragonal distortion which on average results in a cubic atomic structure. The isotropic lattice strain is a result of atom-pair-dependent bond lengths, following the trend d Au—Au > d Au—Cu > d Cu—Cu, highlighted by density functional theory calculations. This approach is generalizable and should be extensible to other disordered systems, allowing for quantification of localized structure deviations.

scholarly journals Influence of a Cu-Zirconia Interface Structure on CO2 Adsorption and Activation

2021 ◽  
Author(s):  
Lars Gell ◽  
Aku Lempelto ◽  
toni Kiljunen ◽  
Karoliina Honkala
Keyword(s):  
Density Functional Theory ◽  
Chemical Composition ◽  
Atomic Structure ◽  
Density Functional ◽  
Co2 Adsorption ◽  
Density Functional Theory Calculations ◽  
Interface Structure ◽  
Functional Theory ◽  
Binding Strength ◽  
Interface Structures

We have screened different Cu-ZrO<sub>2</sub> interface structures and analysed the influence of the interface structure on CO<sub>2</sub> binding strength using density functional theory calculations. Our results demonstrate that a Cu nanorod favours one position on both tetragonal and monoclinic ZrO<sub>2</sub> surfaces, where the bottom Cu atoms are placed close the lattice oxygens. CO<sub>2</sub> prefers a bent bidentate configuration at the interface and the molecule is clearly activated being negatively charged. Altogether, our results highlight that CO<sub>2</sub> adsorption and activation depend sensitively on the chemical composition and atomic structure of the interface used in the calculations. <div><br></div>

scholarly journals Influence of a Cu-Zirconia Interface Structure on CO2 Adsorption and Activation

2021 ◽  
Author(s):  
Lars Gell ◽  
Aku Lempelto ◽  
toni Kiljunen ◽  
Karoliina Honkala
Keyword(s):  
Density Functional Theory ◽  
Chemical Composition ◽  
Atomic Structure ◽  
Density Functional ◽  
Co2 Adsorption ◽  
Density Functional Theory Calculations ◽  
Interface Structure ◽  
Functional Theory ◽  
Binding Strength ◽  
Interface Structures

We have screened different Cu-ZrO<sub>2</sub> interface structures and analysed the influence of the interface structure on CO<sub>2</sub> binding strength using density functional theory calculations. Our results demonstrate that a Cu nanorod favours one position on both tetragonal and monoclinic ZrO<sub>2</sub> surfaces, where the bottom Cu atoms are placed close the lattice oxygens. CO<sub>2</sub> prefers a bent bidentate configuration at the interface and the molecule is clearly activated being negatively charged. Altogether, our results highlight that CO<sub>2</sub> adsorption and activation depend sensitively on the chemical composition and atomic structure of the interface used in the calculations. <div><br></div>

In search of non-conventional surface oxidic motifs of Cu on Au(111)

2016 ◽  
Vol 18 (10) ◽  
pp. 7349-7358 ◽  
Author(s):  
Taehun Lee ◽  
Yonghyuk Lee ◽  
Kisung Kang ◽  
Aloysius Soon
Keyword(s):  
Density Functional Theory ◽  
Atomic Structure ◽  
First Principles ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Functional Theory ◽  
System P ◽  
Surface Energetics

Using first-principles density-functional theory calculations, we systematically examine and analyze the detailed atomic structure and surface energetics of various oxidic motifs of Cu on Au(111), in search of new non-conventional, non-hexagonal surface oxidic structures in this system.

scholarly journals ATOMIC STRUCTURE OF THE SI(47 35 7) SURFACE

2020 ◽  
Author(s):  
Ruslan Zhachuk ◽  
Andrey Dolbak ◽  
Aleksandr Shklyaev
Keyword(s):  
Experimental Data ◽  
Density Functional Theory ◽  
Atomic Structure ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
High Index ◽  
Atomic Model ◽  
Functional Theory

The atomic structure of clean high-index Si(47 35 7) surface is studied. The atomic model of this surface is proposed based on density functional theory calculations and experimental data

Is a Non-Transition Element Nitride Ferromagnet Ever Achievable? Indication of the N-N Pairing Instability

2006 ◽  
Vol 71 (11-12) ◽  
pp. 1525-1531 ◽  
Author(s):  
Wojciech Grochala
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Transition Element ◽  
Density Functional Theory Calculations ◽  
Functional Theory

The enthalpy of four polymorphs of CaN has been scrutinized at 0 and 100 GPa using density functional theory calculations. It is shown that structures of diamagnetic calcium diazenide (Ca2N2) are preferred over the cubic ferromagnetic polymorph (CaN) postulated before, both at 0 and 100 GPa.

scholarly journals Tensor-structured algorithm for reduced-order scaling large-scale Kohn–Sham density functional theory calculations

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Chih-Chuen Lin ◽  
Phani Motamarri ◽  
Vikram Gavini
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Large Scale ◽  
Density Functional Theory Calculations ◽  
System Size ◽  
Real Space ◽  
Functional Theory ◽  
Reduced Order ◽  
Separable Approximation ◽  
Tensor Basis

AbstractWe present a tensor-structured algorithm for efficient large-scale density functional theory (DFT) calculations by constructing a Tucker tensor basis that is adapted to the Kohn–Sham Hamiltonian and localized in real-space. The proposed approach uses an additive separable approximation to the Kohn–Sham Hamiltonian and an L1 localization technique to generate the 1-D localized functions that constitute the Tucker tensor basis. Numerical results show that the resulting Tucker tensor basis exhibits exponential convergence in the ground-state energy with increasing Tucker rank. Further, the proposed tensor-structured algorithm demonstrated sub-quadratic scaling with system-size for both systems with and without a gap, and involving many thousands of atoms. This reduced-order scaling has also resulted in the proposed approach outperforming plane-wave DFT implementation for systems beyond 2000 electrons.

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