Semi-exact concentric atomic density fitting: Reduced cost and increased accuracy compared to standard density fitting

2014 ◽  
Vol 140 (6) ◽  
pp. 064109 ◽  
Author(s):  
David S. Hollman ◽  
Henry F. Schaefer ◽  
Edward F. Valeev
Keyword(s):  
Atomic Density ◽  
Density Fitting ◽  
Standard Density

scholarly journals Low-Order Scaling G0W0 by Pair Atomic Density Fitting

2020 ◽  
Vol 16 (12) ◽  
pp. 7381-7399
Author(s):  
Arno Förster ◽  
Lucas Visscher
Keyword(s):  
Atomic Density ◽  
Density Fitting ◽  
Low Order

Fast construction of the exchange operator in an atom-centred basis with concentric atomic density fitting

2017 ◽  
Vol 115 (17-18) ◽  
pp. 2065-2076 ◽  
Author(s):  
David S. Hollman ◽  
Henry F. Schaefer ◽  
Edward F. Valeev
Keyword(s):  
Atomic Density ◽  
Density Fitting ◽  
Exchange Operator

scholarly journals Efficient evaluation of exact exchange for periodic systems via concentric atomic density fitting

2020 ◽  
Vol 153 (12) ◽  
pp. 124116
Author(s):  
Xiao Wang ◽  
Cannada A. Lewis ◽  
Edward F. Valeev
Keyword(s):  
Atomic Density ◽  
Periodic Systems ◽  
Density Fitting ◽  
Exact Exchange

Use of backscattered electron image intensity signals to calculate the water/cement ratio of concrete

1992 ◽  
Vol 50 (1) ◽  
pp. 356-357
Author(s):  
R. J. Lee ◽  
A. J. Schwoeble ◽  
Yuan Jie
Keyword(s):  
Reliable Data ◽  
X Ray ◽  
Rapid Measurement ◽  
Trained Personnel ◽  
Electron Image ◽  
Backscattered Electron ◽  
Production Period ◽  
Strength And Durability ◽  
Automated Procedures ◽  
Standard Density

Water/Cement (W/C) ratio is a very important parameter affecting the strength and durability of concrete. At the present time, there are no ASTM methods for determining W/C ratio of concrete structures after the production period. Existing techniques involving thin section standard density comparative associations using light optical microscopy and rely on visual comparisons using standards and require highly trained personnel to produce reliable data. This has led to the exploration of other methods utilizing automated procedures which can offer a precise and rapid measurement of W/C ratio. This paper discusses methods of determining W/C ratio using a scanning electron microscope (SEM) backscattered electron image (BEI) intensity signal and x-ray computer tomography.

scholarly journals Fast periodic Gaussian density fitting by range separation

2021 ◽  
Vol 154 (13) ◽  
pp. 131104
Author(s):  
Hong-Zhou Ye ◽  
Timothy C. Berkelbach
Keyword(s):  
Gaussian Density ◽  
Density Fitting

scholarly journals Intercalated architecture of MA2Z4 family layered van der Waals materials with emerging topological, magnetic and superconducting properties

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Lei Wang ◽  
Yongpeng Shi ◽  
Mingfeng Liu ◽  
Ao Zhang ◽  
Yi-Lun Hong ◽  
...  
Keyword(s):  
Electronic Properties ◽  
Density Functional ◽  
Layer Structure ◽  
Atomic Layer ◽  
Type I ◽  
Hybrid Functional ◽  
Functional Theory ◽  
Valence Electrons ◽  
Nonmagnetic Metals ◽  
Standard Density

AbstractThe search for new two-dimensional monolayers with diverse electronic properties has attracted growing interest in recent years. Here, we present an approach to construct MA2Z4 monolayers with a septuple-atomic-layer structure, that is, intercalating a MoS2-type monolayer MZ2 into an InSe-type monolayer A2Z2. We illustrate this unique strategy by means of first-principles calculations, which not only reproduce the structures of MoSi2N4 and MnBi2Te4 that were already experimentally synthesized, but also predict 72 compounds that are thermodynamically and dynamically stable. Such an intercalated architecture significantly reconstructs the band structures of the constituents MZ2 and A2Z2, leading to diverse electronic properties for MA2Z4, which can be classified according to the total number of valence electrons. The systems with 32 and 34 valence electrons are mostly semiconductors. Whereas, those with 33 valence electrons can be nonmagnetic metals or ferromagnetic semiconductors. In particular, we find that, among the predicted compounds, (Ca,Sr)Ga2Te4 are topologically nontrivial by both the standard density functional theory and hybrid functional calculations. While VSi2P4 is a ferromagnetic semiconductor and TaSi2N4 is a type-I Ising superconductor. Moreover, WSi2P4 is a direct gap semiconductor with peculiar spin-valley properties, which are robust against interlayer interactions. Our study thus provides an effective way of designing septuple-atomic-layer MA2Z4 with unusual electronic properties to draw immediate experimental interest.

scholarly journals Intermolecular electrostatic energies using density fitting

2005 ◽  
Vol 123 (4) ◽  
pp. 044109 ◽  
Author(s):  
G. Andrés Cisneros ◽  
Jean-Philip Piquemal ◽  
Thomas A. Darden
Keyword(s):  
Density Fitting
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