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Validation of density functionals for transition metals and intermetallics using data from quantitative electron diffraction
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DOI：10.1063/1.4792436.png)
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Abstract
En 中文
Accurate low-order structure factors (F-g) measured by quantitative convergent beam electron diffraction (QCBED) were used for validation of different density functional theory (DFT) approximations. Twenty-three low-order F-g were measured for the transition metals Cr, Fe, Co, Ni, and Cu, and the transition metal based intermetallic phases gamma-TiAl, beta-NiAl, and gamma(1)-FePd using a multi-beam off-zone axis QCBED method and then compared with F-g calculated by ab initio DFT using the local density approximation (LDA) and LDA + U, and different generalized gradient approximations (GGA) functionals. Different functionals perform very differently for different materials and crystal structures regarding prediction of low-order F-g. All the GGA functionals tested in the paper except for EV93 achieve good overall agreement with the experimentally determined low-order F-g for BCC Cr and Fe, while EV93 performs the best for FCC Ni and Cu. The LDA and GGA functional fail to predict accurately the low-order F-g for beta-NiAl and gamma(1)-FePd. The LDA + U approach, through tuning of U, can achieve excellent matches with the experimentally measured F-g for all the metallic systems investigated in this paper. The use of experimentally accessible low order F-g as an additional set of metrics in approaches of validation of DFT calculations is discussed and has potential to assist in and to stimulate development of improved functionals. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4792436]
Keywords:
GENERALIZED GRADIENT APPROXIMATION
DEBYE-WALLER FACTORS
CHARGE-DENSITY
X-RAY
TEMPERATURE FACTORS
PRECISE
REFINEMENT
EXCHANGE
SOLIDS
NIO
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