Papers by Author: Long Qing Chen

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Authors: Veeramuthu Vaithianathan, C. Wolverton, Long Qing Chen
Abstract: This short article reports our recent effort to integrate the mesoscale phase-field method with first-principles total energy calculations, linear response theory, as well as mixedspace cluster expansion. A particular example of applying such a multiscale approach to the case of precipitation of semicoherent θ' particles in an Al-matrix is presented.
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Authors: Tae Wook Heo, Saswata Bhattacharyya, Long Qing Chen
Abstract: A phase-field model is described for predicting the diffusional phase transformation process in elastically inhomogeneous polycrystals. The elastic interactions are incorporated by solving the mechanical equilibrium equation using the Fourier-spectral iterative-perturbation scheme taking into account elastic modulus inhomogeneity. A number of examples are presented, including grain boundary segregation, precipitation of second-phase particles in a polycrystal, and interaction between segregation at a grain boundary and coherent precipitates inside grains. It is shown that the local pressure distribution due to coherent precipitates leads to highly inhomogeneous solute distribution along grain boundaries.
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Authors: Manjeera Mantina, Long Qing Chen, Zi Kui Liu
Abstract: A simplified approach to predicting diffusion coefficients directly from first-principles is proposed. In this approach, the atomic jump frequencies are calculated through the Eyring’s reaction rate theory while the temperature dependence of diffusion coefficients are accounted using phonon theory within the quasi-harmonic approximation. The procedure can be applied to both self-diffusion and impurity diffusion coefficients and different crystal systems. Applications to self-diffusion coefficients in fcc Cu, bcc Mo, hcp Mg and impurity diffusion coefficients of Li in fcc Al, W in bcc Mo and Cd in hcp Mg show agreement with experimental measurements.
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