{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

# 10 - Chemistry 1000 Lecture 10 Crystal structures(continued...

This preview shows pages 1–5. Sign up to view the full content.

Chemistry 1000 Lecture 10: Crystal structures (continued) Marc R. Roussel

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Packing fraction I Recall: For rectangular lattices I A corner atom is shared between 8 unit cells 1 8 of an atom is inside any given cell. I A facial atom is shared between 2 unit cells 1 2 of an atom is inside any given cell. I For the bcc lattice, we have 8 × 1 8 + 1 = 2 atoms.
I The diagonal of the bcc unit cell = 4 r . D a a a 4 r x C B A I In the triangle ABC, x 2 = a 2 + a 2 = 2 a 2 . I In the triangle ACD, x 2 = (4 r ) 2 - a 2 . I Combining the two equations, we get 2 a 2 = 16 r 2 - a 2 , or r = 3 4 a . I The atoms occupy 2 atoms × 4 3 π r 3 = π 3 8 a 3 . I Since the total volume of the unit cell is a 3 , the fraction of the unit cell occupied by atoms is π 3 8 = 0 . 68.

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Examples 1. Silver has an fcc lattice with a unit cell whose lattice constant is 4 . 0862 × 10 - 10 m. Calculate (a) the metallic radius, and (b) the density. Answers: (a) 1 . 4447 × 10 - 10 m, (b) 10 501 kg m - 3 2. Barium has a bcc lattice with a unit cell edge length of 502.5 pm. Calculate (a) the metallic radius, and (b) the
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### Page1 / 10

10 - Chemistry 1000 Lecture 10 Crystal structures(continued...

This preview shows document pages 1 - 5. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online