In a hexagonal close-packed (HCP) structure, how many atoms are present in one u

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Question: In a hexagonal close-packed (HCP) structure, how many atoms are present in one unit cell? (2023)

Options:

Correct Answer: 6

Exam Year: 2023

Solution:

In a hexagonal close-packed (HCP) structure, there are 6 atoms per unit cell.

In a hexagonal close-packed (HCP) structure, how many atoms are present in one unit cell? (2023)

In a hexagonal close-packed (HCP) structure, how many atoms are present in one unit cell? (2023)

Step 1: Understand what a unit cell is. A unit cell is the smallest repeating unit in a crystal structure.
Step 2: Recognize that the hexagonal close-packed (HCP) structure has a specific arrangement of atoms.
Step 3: Identify the positions of atoms in the HCP structure. There are atoms at the corners and in the center of the hexagonal faces.
Step 4: Count the atoms at the corners of the hexagon. There are 12 corner atoms, but each corner atom is shared by 6 unit cells, so they contribute 12/6 = 2 atoms.
Step 5: Count the atoms in the center of the top and bottom hexagonal faces. There are 2 face-centered atoms, and each is fully contained in the unit cell, contributing 2 atoms.
Step 6: Count the 2 atoms located in the center of the unit cell. These are fully contained in the unit cell, contributing 2 atoms.
Step 7: Add the contributions together: 2 (from corners) + 2 (from faces) + 2 (from center) = 6 atoms in total.

Hexagonal Close-Packed Structure – The HCP structure is a type of crystal lattice arrangement where atoms are closely packed in a hexagonal formation, resulting in a specific number of atoms per unit cell.