There’s plenty of room at the grain boundary (GB), in which we can manipulate its energy and structure for particular properties in polycrystalline materials. Recently, we observed that the aesthetic of the room quantified by the electrical conductance was changed dramatically by simply by turning on/off a UV laser. Specifically, based on photoelectron spectroscopy and complementary conductive atomic force microscopy, we demonstrate that the hundredfold increases in the electrical conductance measured at the GB are strongly associated with the ultraviolet-induced oxygen vacancies, and thus offering novel strategies for optoelectronic or neuromorphic computing applications. Historically, it is a challenge to optimize the room especially in the case of body-centered cubic (bcc) metals due to the lack of quantitative relations between GB energies and populations or microstructure-property-processing relationships. Here, we present a universal function for computing the energies of arbitrary GBs in the bcc metals. The effectiveness of the universal function in describing the variations of the GB energies is demonstrated by consistency between the output of the function and the energies of ~ 2,500 GBs simulated by the embedded atom method. Large-scale comparisons between the interpolated energies and measured GB populations reveal that the population distributions are governed by local energy minima located at the Σ1, Σ3, Σ9, Σ11, and Σ33a misorientations, representing a major step forward for the GB engineering of bcc metals.
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