# Miller indices question

Entropia
I am new to understanding Miller indices (its never been covered in a class that i have taken etc) and there is a notation that i am seeing in the scientific literature that i don't understand. -Its the notation used after the (h,k,l) numbers. here are a few examples (I put in bold print the bit that I don't understand):

Ge(100)-2 x 1

Ge(111)-2 x 8

S/Ge(111)-2 x 2

I have looked at various intro to miller indices type of sites, but none of them make any mention of what the notation means after the (h,k,l) notation.

## Answers and Replies

Homework Helper
I assume that it is the offset in the unit cell. If I find a link I'll edit it in, but let me just give the justification for the need for this sort of thing.

As an example, consider NaCl. The (001) surface is always parallel, but its chemical composition could be either a plane of sodium atoms, or a plane of Chlorine atoms.

Nope, it turns out that the N x M defines a surface that violates the crystal symmetry in a N x M pattern. Here's a link:

"Real Surfaces"
http://www.cem.msu.edu/~cem924sg/LectureNotes.html

Thanks for the learning.

Carl

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Entropia

I am still confused though. The explanation in the miller indices section of the link only talks about simple miller indices notation, and the notation for stepped surfaces (not so simple).

I did not find anything that fits the pattern for the miller indices notation that i am extremely confused about.

Or, did I miss something?

Thanks! :)

Entropia
Miller Indices!

Help!

I have searched through countless sites and I have yet to find an explanation on this.

I have come across some Miller Indices notation (in the scientific literature) that I do not understand and its torturing me to not be able to understand! Below are a few examples, I don't understand the bit that I put in bold:

Ge(100)-2 x 1

Ge(111)-2 x 8

S/Ge(111)-2 x 2

Can anybody explain to me what that part of the Miller Indices notation means, or point me to a source that explains it?

Staff Emeritus
Miller indices - http://www.chem.qmul.ac.uk/surfaces/scc/scat1_1b.htm [Broken]

The 2x1, 2x8 and 2x2 are not Miller indices. What is the source of these numbers?

Also - http://www.gly.uga.edu/schroeder/geol6550/millerindices.html [Broken]

http://www.keele.ac.uk/depts/ch/resources/xtal/miller.html [Broken]

Here is a discussion of (2x1) and (2x2) surfaces with use of Miller indices - http://alpdmn.phys.psu.edu/LEED.html

It appears to be a different way of discussing a group of atoms in a crystal plane.

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Entropia
the last link is the kind of thing i was looking for!

thank you SO MUCH!

i understand what it meant by that notation now.

Staff Emeritus