Abstract
A new Nb–silicide, δ-Nb11Si4, identified as a second phase precipitated from a Nb–Si solid solution, was characterized by combining crystallographic analysis with first-principles calculations. The crystal structure was determined as a body-centered orthorhombic system with space group Immm using transmission electron microscope (TEM). Based on the crystallographic relationship between the δ and Nb phases, // {200}Nb and // ⟨001⟩Nb, eight possible unit cells were proposed, which were optimized by first-principles calculations. By analyzing the experimental and calculated data, we obtained the final unit cell of the δ phase, which was confirmed by high-resolution TEM images. In addition, density of states and electron density difference of δ-Nb11Si4 revealed that the δ structure was in a metastable state at low temperature because not all the bonding states were filled.
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