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Engineering Exams RRB-JE CS (Chemical Supervisor - Research) Technical Abilities 2025 22.04.25 Paper-2 Shift-2 Easy +1 -0.33
Which of the following are the Miller Indices of a close packed plane in the FCC crystal?
Correct Answer: D. -111
Explanation: In a Face-Centered Cubic (FCC) crystal, the close-packed planes are the {111} family. These planes have the highest atomic packing density because they consist of atoms arranged in a triangular, nestled pattern that maximizes space efficiency. In a unit cell, these planes intersect the x, y, and z axes at equal distances (or their negatives), resulting in Miller indices such as (111), (-111), (1-11), and (11-1). Because the atoms are most tightly packed along these specific crystallographic orientations, they are the primary planes for slip and deformation in FCC materials. Therefore, among the given choices, -111 represents a member of this close-packed family.
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