Validation of density functionals for transition metals and intermetallics using data from quantitative electron diffraction

作者：Sang, Xiahan^*; Kulovits, Andreas; Wang, Guofeng; Wiezorek, Joerg

来源：Journal of Chemical Physics, 2013, 138(8): 084504.

DOI：10.1063/1.4792436

• GENERALIZED GRADIENT APPROXIMATION
• DEBYE-WALLER FACTORS
• CHARGE-DENSITY
• X-RAY
• TEMPERATURE FACTORS
• PRECISE
• REFINEMENT
• EXCHANGE
• SOLIDS
• NIO

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.

• 出版日期2013-2-28