Question
Download Solution PDFIf the radius of an in a close-packed hexagonal crystal is r, the length of the edge of the unit cell a is:
Answer (Detailed Solution Below)
Detailed Solution
Download Solution PDFExplanation:
Hexagonal Close-Packed (HCP) Crystal Structure
Definition: The hexagonal close-packed (HCP) crystal structure is one of the most efficient ways of arranging spheres in a solid, allowing atoms to pack together as closely as possible. In this structure, each atom has 12 nearest neighbors, and the atoms are packed in such a way that the distances between them are minimized.
Characteristics of various types of structures are shown in the table below:
|
Characteristics |
BCC |
FCC |
HCP |
|
a to r relation |
\(a = \frac{{4r}}{{√ 3 }}\) |
\(a = 2√ 2 r\) |
\(a = 2r\) |
|
The average number of atoms |
2 |
4 |
6 |
|
Coordination number |
8 |
12 |
12 |
|
APF |
0.68 |
0.74 |
0.74 |
|
Examples |
Na K V Mo Ta W |
Ca Ni Cu Ag Pt Au Pb Al |
Be Mg Zn Cd Te |
Last updated on May 20, 2025
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