Metastable precipitate phase boundaries are difficult to ascertain experimentally and yet are important for controlling the microstructure of precipitation-hardenable alloys. We demonstrate how first-principles calculations of configurational and vibrational free energies can be used to predict precipitate phase boundaries of stable and metastable phases in Al–Cu alloys. Surprisingly, the formation entropy of a Cu impurity is found to be hugely positive(+2.7 k B /atom), leading to a dramatic enhancement in the solubility. The large entropy is dominated by the very low-frequency vibration of the small impurity atom (Cu) inside the large cage of the host (Al). The agreement between the GGA and experimental data is within 100 K for all phases, showing that accurate first-principles determination of metastable phase boundaries is now possible.
Description
Predicting metastable phase boundaries in Al–Cu alloys from first-principles calculations of free energies: The role of atomic vibrations
%0 Journal Article
%1 0295-5075-73-5-719
%A Ravi, C.
%A Wolverton, C.
%A Ozoliņš, V.
%D 2006
%J EPL (Europhysics Letters)
%K ab initio meta-stable phase thermodynamics
%N 5
%P 719
%T Predicting metastable phase boundaries in Al–Cu alloys from first-principles calculations of free energies: The role of atomic vibrations
%U http://stacks.iop.org/0295-5075/73/i=5/a=719
%V 73
%X Metastable precipitate phase boundaries are difficult to ascertain experimentally and yet are important for controlling the microstructure of precipitation-hardenable alloys. We demonstrate how first-principles calculations of configurational and vibrational free energies can be used to predict precipitate phase boundaries of stable and metastable phases in Al–Cu alloys. Surprisingly, the formation entropy of a Cu impurity is found to be hugely positive(+2.7 k B /atom), leading to a dramatic enhancement in the solubility. The large entropy is dominated by the very low-frequency vibration of the small impurity atom (Cu) inside the large cage of the host (Al). The agreement between the GGA and experimental data is within 100 K for all phases, showing that accurate first-principles determination of metastable phase boundaries is now possible.
@article{0295-5075-73-5-719,
abstract = {Metastable precipitate phase boundaries are difficult to ascertain experimentally and yet are important for controlling the microstructure of precipitation-hardenable alloys. We demonstrate how first-principles calculations of configurational and vibrational free energies can be used to predict precipitate phase boundaries of stable and metastable phases in Al–Cu alloys. Surprisingly, the formation entropy of a Cu impurity is found to be hugely positive(+2.7 k B /atom), leading to a dramatic enhancement in the solubility. The large entropy is dominated by the very low-frequency vibration of the small impurity atom (Cu) inside the large cage of the host (Al). The agreement between the GGA and experimental data is within 100 K for all phases, showing that accurate first-principles determination of metastable phase boundaries is now possible.},
added-at = {2010-11-03T17:57:04.000+0100},
author = {Ravi, C. and Wolverton, C. and Ozoliņš, V.},
biburl = {https://www.bibsonomy.org/bibtex/2e836185643475d5ec4a6c836f865697f/riche.ma},
description = {Predicting metastable phase boundaries in Al–Cu alloys from first-principles calculations of free energies: The role of atomic vibrations},
interhash = {5def21f9092cda8c7a8e66f11c37133a},
intrahash = {e836185643475d5ec4a6c836f865697f},
journal = {EPL (Europhysics Letters)},
keywords = {ab initio meta-stable phase thermodynamics},
number = 5,
pages = 719,
timestamp = {2010-11-03T17:57:04.000+0100},
title = {Predicting metastable phase boundaries in Al–Cu alloys from first-principles calculations of free energies: The role of atomic vibrations},
url = {http://stacks.iop.org/0295-5075/73/i=5/a=719},
volume = 73,
year = 2006
}