# Electron diffraction lab help

• quietrain
In summary, the conversation discusses using Bragg's law to determine the interplanar distance of graphite carbon and the possibility of determining the interatomic distance between carbon atoms on the same plane. It is mentioned that the structure-factor and orthorhombic unit cell can help in finding the interatomic distance, and that multiple diffraction rings may be needed to accurately determine it. The structure of graphite, with its hexagonal shape and 120 degree bond angles, is also mentioned as a factor in determining the interatomic distance.

#### quietrain

ok, i did a lab and found values of the diameter of the electron rings after diffraction from a graphite. i also have the voltage that i accelerate the electrons to hit the graphite.

so to find the distance between adjacent planes of graphite carbon "d", we use bragg's diffraction law right? 2dsin(theta) = n(lamda)

but the problem is what if i need to find the interatomic distance "a" between the carbon atoms on the same plane. is there some sort of equation or law i can use to find this distance from the experiment data that i obtained above? i don't seem to recall any.

and also, am i right to say, the outer diffraction ring is caused by the diffraction between atoms of the same plane (interatomic) whereas the inner diffraction ring is caused by the diffraction between layers of atoms "d" given by bragg's law?

thanks a ton!

maybe i rephrase my question

ok, we use bragg's law to determine the spacing d between LAYERS of graphite

but how do we determine the interatomic spacing A between the individual Carbon atoms for each plane of individual graphite?

anyone knows?

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quietrain,

Graphite is pretty simple when it comes to determining the structure-factor. I won't solve the problem for you, but try to represent graphite in terms of a orthorhombic unit-cell with a multi-atom basis. Find the structure-factor based on that symmetry. There is no easy "plug and chug" answer for this problem. Your going to need to do some work!

modey3

er i know the bond angles are 120 and the interatomic distance is around 0.142nm. but how do i get the interatomic distance from an experiment? i only have values for voltage, and the electron ring diffraction diameter only?

so with this 2 variables, i can find the interplanar distance d using bragg's law. but what about the interatomic distance? can i find it from just those 2 variables?

quietrain,

You will need to use more than just one diffraction ring to determine the inter-atomic distance. That's why you need to determine the structure-factor.

modey3

oh ya... i have 2 radius of diffraction rings... one bigger than the other... but i don't understand why there are two?

what is the structure? i only know that graphite is hexagonal in shape, so they have bond angles of 120?

but how does that allow me to find the interatomic distance?

## 1. What is electron diffraction and why is it important in the lab?

Electron diffraction is a technique used to study the structure of materials at the atomic scale. It involves shooting a beam of electrons at a sample and analyzing the resulting pattern of diffracted electrons. This technique is important in the lab because it allows us to understand the arrangement of atoms in a material, which is crucial in fields such as materials science and nanotechnology.

## 2. How does electron diffraction differ from other diffraction techniques?

Electron diffraction differs from other diffraction techniques, such as X-ray diffraction, in that it uses a beam of electrons instead of photons. This allows for a higher resolution and the ability to study smaller structures. Additionally, electron diffraction can be used to study non-crystalline materials, whereas X-ray diffraction is limited to crystalline materials.

## 3. What equipment is needed to perform an electron diffraction experiment?

To perform an electron diffraction experiment, you will need an electron source (such as a cathode ray tube or an electron gun), a sample holder, a vacuum chamber, and a detector to capture the diffracted electrons. Additional equipment may include lenses and apertures to control the electron beam and a computer for data analysis.

## 4. What are some common applications of electron diffraction?

Electron diffraction has a wide range of applications, including materials analysis, crystallography, and biological imaging. It is commonly used in fields such as materials science, chemistry, and physics to study the atomic structure of various materials. In biology, electron diffraction is used to determine the structure of biomolecules, such as proteins and DNA.

## 5. What are some potential sources of error in an electron diffraction experiment?

Some potential sources of error in an electron diffraction experiment include sample contamination, improper alignment of the beam and detector, and instrumental noise. Sample preparation is also crucial, as any defects or impurities in the sample can affect the diffraction pattern. Additionally, the electron beam intensity and voltage must be carefully controlled to avoid overexposure or underexposure, which can also lead to errors in the data.