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Iowa State University

Engineering Physics

2003

Duane D. Johnson

Articles 1 - 3 of 3

Full-Text Articles in Physics

Prediction Of Dopant Ionization Energies In Silicon: The Importance Of Strain, A. Rockett, Duane D. Johnson, S. V. Khare, B. R. Tuttle Dec 2003

Prediction Of Dopant Ionization Energies In Silicon: The Importance Of Strain, A. Rockett, Duane D. Johnson, S. V. Khare, B. R. Tuttle

Duane D. Johnson

Based on a hydrogenic state and strain changes upon defect charging, we propose a simple, parameter-free model that agrees well with the observed group III and V monovalent-impurity ionization energies in Si, revealing the importance of such strain effects. Changes in lattice strain upon defect charging are obtained via superposition and elasticity theory using atomic relaxations from density functional theory.


Competition Between Ferromagnetism And Antiferromagnetism In Fept, G. Brown, B. Kraczek, A. Janotti, T. C. Schulthess, G. M. Stocks, Duane D. Johnson Aug 2003

Competition Between Ferromagnetism And Antiferromagnetism In Fept, G. Brown, B. Kraczek, A. Janotti, T. C. Schulthess, G. M. Stocks, Duane D. Johnson

Duane D. Johnson

Ni/Fe/Co/Cu(100) films were epitaxially grown and investigated by photoemission electron microscopy. The magnetic correlation of the Ni and Co films was investigated by element-specific domain images. We found that the Ni magnetization exhibits a continuous rotation in the spin reorientation transition (SRT) region and that the Ni SRT thickness oscillates with the Fe film thickness.


Reply To “Comment On ‘Classical Density Functional Theory Of Freezing In Simple Fluids: Numerically Induced False Solutions’ ”, M. Valera, F. J. Pinski, Duane D. Johnson May 2003

Reply To “Comment On ‘Classical Density Functional Theory Of Freezing In Simple Fluids: Numerically Induced False Solutions’ ”, M. Valera, F. J. Pinski, Duane D. Johnson

Duane D. Johnson

Recently we solved, via discrete numerical grids, the Ramakrishna-Yossouff density-functional theory equations for the freezing transition and obtained an intricate phase diagram of hard-sphere mixtures. Even though such methods provide more variational freedom than basis-set methods, we found that the thermodynamic quantities were sensitive to the spacing of numerical grids employed and observed numerically induced false minima. Dasgupta and Valls have commented that these false minima were due to our use of k-space methods and, hence, their early works based on a fully r-space approach are qualitatively correct, despite also being sensitive to the mesh granularity. Here, we clarify the …