Register to reply

Lattice Constant of Iron

by mjordan2nd
Tags: constant, iron, lattice
Share this thread:
Jan25-11, 07:05 PM
P: 122
1. The problem statement, all variables and given/known data

The density of bcc iron is 7900 kg/m3, and its atomic wieght is 56 amu. Using this information, calculate the lattice constant of iron's cubic unit cell and the interatomic spacing (i.e. nearest neighbor distance).

2. Relevant equations

3. The attempt at a solution

I thought this was mostly unit conversion, with the only relevant knowledge being that there are 2 atoms per cubic unit cell.

7900 kg/m^3 = 4.757*10^30 amu/m^3
4.757*10^30 amu/m^3 = 8.49552*10^28 atoms of iron / m^3
8.49552*10^28 atoms of iron / m^3 = 4.396057*10^9 atoms of iron / m
4.396057*10^9 atoms of iron / m = 0.439606 atoms of iron / angstrom

Taking the reciprocal of the final answer should get us the space between atoms, which gives me 2.27 angstroms between atoms of iron. I thought this should be the lattice constant, however I'm guessing I've done something wrong since I believe the answer should be 2.86 angstroms.

Any help would be appreciated. Thanks.
Phys.Org News Partner Science news on
Wearable 4MM jetpack tested on speed, agility for runners (w/ Video)
How did evolution optimize circadian clocks?
Corn spots: Study finds important genes in defense response
Jan26-11, 11:09 AM
P: 122
Nevermind, I figured it out. In case anyone is interested, the density of a conventional cubic cell is going to be

[tex]\frac{112 AMU}{a^3}[/tex]

since the bcc lattice has to lattice points in a conventional cell. This must be equated with 7900 Kg/m^3. After conversion through dimensional analysis, you solve for a, which is the lattice parameter.

Register to reply

Related Discussions
Lattice Constant Advanced Physics Homework 20
Braggs law: lattice constant Atomic, Solid State, Comp. Physics 4
Lattice constant Advanced Physics Homework 2
Lattice constant of martensite? Atomic, Solid State, Comp. Physics 2
Calculate the lattice constant of a body-centered cubic iron Advanced Physics Homework 1