Gadolinium (Gd) primarily exhibits a hexagonal close-packed (hcp) crystal structure at room temperature. This specific arrangement, often denoted as hP2, is a common and efficient way for atoms to pack together in metallic elements.
Understanding the Hexagonal Close-Packed Structure
The hexagonal close-packed (hcp) structure is characterized by layers of atoms arranged in a hexagonal pattern. Each atom in one layer sits in the depressions formed by three atoms in the layer below it, and the third layer of atoms is directly above the first. This results in a packing efficiency of 74%, which is the highest possible for spheres of uniform size.
For gadolinium, the precise dimensions of this atomic arrangement are defined by its lattice constants:
| Property | Value |
|---|---|
| Crystal Structure | Hexagonal Close-Packed (hcp) (hP2) |
| Lattice Constant 'a' | 363.37 pm (at 20 °C) |
| Lattice Constant 'c' | 578.21 pm (at 20 °C) |
- Lattice Constant 'a': Represents the length of the base vectors in the hexagonal plane.
- Lattice Constant 'c': Represents the height of the unit cell, perpendicular to the hexagonal plane.
These specific lattice constants indicate the precise spacing and arrangement of gadolinium atoms within its crystal lattice at a standard temperature of 20 °C. The hcp structure contributes to many of gadolinium's unique physical properties, including its mechanical strength and magnetic behavior at different temperatures.
