# Me in solving this q

1. Mar 1, 2005

### imran

plz help me in solving this q

obtain an expression for interplanar distance in terms of lattice parameter?

2. Mar 2, 2005

### Gokul43201

Staff Emeritus
This is easy to derive for orthogonal lattices such as a cubic lattice, but harder for other geometries. In the case of an orthogonal geometry, you just have to use the fact that :

$$cos^2 \alpha + cos ^2 \beta + cos ^2 \gamma = 1$$

where $\alpha,~\beta,~\gamma$ are the angles made by a line through the origin to each of the axes. In this case, you make this line be the normal to the plane of interest (ie : its length is the interplanar spacing), and expand each of the cosines in terms of the intercepts on the axes, which in turn come from the Miller Indices of the plane.

3. Mar 3, 2005

### imran

sketch the [110],[222] planes in a cube?

4. Mar 3, 2005

### Gokul43201

Staff Emeritus
What's the problem there ? It's pretty straightforward.