Methods for determination of structure of solid?

In summary, the main methods of determining the structure of a solid to test its genuineness are X-ray diffraction, line spectra, and bombarding the solid with neutrons.
  • #1
strugglin
5
0
Hi, just a basic question , what are the main methods of determining the structure of a solid in order to test its genuinety i.e. gold...
if i were to be given a piece of gold, how would i check that it is genuine gold?

could i use x ray diffraction (If so what measurements /tests would i need to take), line spectra technique etc?
and what destructive methods could i use to figure this out?

thanks!
 
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  • #2
I suppose X-ray diffraction could be used, but it wouldn't be the easiest way. (being that the information gained is more related to the geometric structure than the electronic structure)

But certainly X-rays. XRF, X-ray fluorescence would be my choice. It'd be destructive if you did it on, say, an organic molecule, but not on a lump of metal. Bombard the sucker and look for the characteristic lines of the different elements, basically.
 
  • #3
Tests that use surface tests are not sufficient to differentiate between gold and gold-plated tungsten. Density is a good test but does not rule out tungsten.

X-ray fluorescence is better, but still the x-ray penetration is shallow. The conductivity of gold is much better than tungsten, but because of eddy currents, the test frequency would have to be very low. If you put a gold bar in a solenoid and measure the complex impedance (both inductance and resistive losses) vs frequency, this would be a valid signature (tungsten has twice the bulk resistivity of gold) and can be done quickly (The real and imaginary components of the solenoid impedance are related by the Kramers Kronig relations). I have measured the quality of big (including superconducting) magnets this way down to 5 Hz.

Put a neutron source near gold and activate it to Au-198, which has a 2.7 day half life, and detect the gammas. Neutrons have a very good penetration, and a decay gamma has a 1088 KeV energy (about the best energy for escaping from gold).

Drill a hole through it, or melt it.

[added] One source on the web proposes using large neodymium magnets to make an eddy current test conceptually similar to sliding a neodymium magnet down a copper tube. This would probably require several (2? 4?) large neodymium magnets in a steel frame. The gold would resist sliding through the magnets about 2x more than the tungsten would, but not quite as much as copper or silver.

Bob S
 
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  • #4
Depth profile with secondary ions mass spectrometry.

regards
RJ
 

Related to Methods for determination of structure of solid?

1. What are the most common methods used for determining the structure of a solid?

The most commonly used methods for determining the structure of a solid include X-ray crystallography, neutron diffraction, electron microscopy, nuclear magnetic resonance (NMR), and Fourier transform infrared spectroscopy (FTIR).

2. How does X-ray crystallography work in determining the structure of a solid?

X-ray crystallography involves shining a beam of X-rays onto a crystalline sample, causing the X-rays to diffract and create a unique pattern. This pattern can then be used to determine the arrangement of atoms within the crystal, allowing for the determination of the solid's structure.

3. What is the advantage of using neutron diffraction in structure determination?

Neutron diffraction is advantageous because neutrons have a higher penetration depth than X-rays, allowing for the study of thicker and more complex samples. Additionally, neutrons interact differently with different types of atoms, providing more detailed information about the sample's atomic structure.

4. How does electron microscopy contribute to the determination of solid structure?

Electron microscopy uses a beam of electrons to create an image of a sample, allowing for the visualization of the sample's atomic structure. This method is particularly useful for studying non-crystalline or amorphous solids, which cannot be analyzed using X-ray crystallography.

5. What is the role of NMR and FTIR in determining the structure of a solid?

NMR and FTIR are spectroscopic techniques that can provide information about the chemical bonds and functional groups present in a solid, which can in turn help determine its structure. NMR is particularly useful for studying the structure of organic compounds, while FTIR is commonly used for identifying functional groups in inorganic solids.

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