# What's the meaning of the Cartesian coordinates of the atom?

1. Jan 10, 2006

### zsglly

How to get the Cartesian coordinates of an atom?

Dear friends,
Such a question confused me when reading!
"xi,yi and zi are the Cartesian coordinates of the ith atom"
How to get the coordinate of an atom? For example: carbon, oxygen?
I think the atom is only a dot! What's the way to indicate it with Cartesian coordinate?
Thank you!!
Sincerely,
zsglly

Last edited: Jan 10, 2006
2. Jan 10, 2006

### lightgrav

They're telling you the coordinate of the atom's center-of-mass
(we always describe the location of an object by its c.o.m. location!).
The C atom is at ( x_c , y_c , z_c ) ; the O atom is at ( x_o , y_o , z_o ) .

3. Jan 10, 2006

### zsglly

But I need the specific numerical value for calculating.
How to get it?

4. Jan 10, 2006

### lightgrav

Well, if they're not given in the problem, choose:
a) the text might list some inter-atom spacings in the chapter
b) you're supposed to keep them as variables (x,y,z)

What are you supposed to be calculating / computing ?

5. Jan 10, 2006

### zsglly

Until now, I didn't find any text about inter-atom spacings
To calculate moments of inertia.
I only want to get the value of several atoms.

Last edited: Jan 10, 2006
6. Jan 11, 2006

### zsglly

Actually, I'm not sure whether I need calculate the Cartesian coordinates or not. But I hope not. Because my only intention is to get the value of carbon, oxygen and so on.

7. Jan 11, 2006

### Gokul43201

Staff Emeritus
Of what ??? ( For instance, a carbon dioxide molecule about an axis perpendicular to the molecular axis ?) Please write down the given question completely. You have not provided enough information.

8. Jan 11, 2006

### algebra_chem

are you trying to say something like:
how many atoms does a carbon or oxygen have????

9. Jan 28, 2006

### zsglly

To calulate the moment of inertia using J.O. Hirshfelder's method
Do you know?