title
Sorry in advance if I use the wrong flair for this post. There was no "metallurgy" or "materials science" tag
I'm a coin collector. And I've seen silver and gold in grades ranging from "looks like someone ran this over with a car for pleasure", to mirror like deep proof finishes on certain coins and bullion.
I understand most coins aren't "polished," to achieve that mirror like effect you see in some high grade bullion or mint state coins. It's the die pressing to create a very shiny field.
But that's about all I know.
When metal is shiny verses when it looks "rough" like mild steel vs .999 silver, what exactly is happening to the lattice structure of the crystal matrices to create the gradient from rough or "satin" to mirror like?
Are the rough crystal edges being compressed enough to push the molecules closer together to reflect light rather than refract it?
Sorry if not much of that made sense. English isn't my first language... No it is I'm just kind of dumb.
Thanks in advance!
What am I?
Edit: I was given a hint, the phrase "a mirror's guide" is now replaced by "woe by mirror"
Topochemical halide ion replacement in lanthanide oxyiodide nanostructures proceeds with complete preservation of the tetragonal matlockite crystal structure along a gradient of increasing anion hardness. Reformation of the anion lattice around the intact cation slabs impedes 5D3-5D4 phonon-assisted cross relaxation and is observed as a distinctive blue hue for an embedded quantum reporter.
Abstract
A challenge in anion control in periodic solids is to preserve the crystal lattice while substituting for different anions of widely varying size and hardness. Post-synthetic modification routes that place cations or anions in non-equilibrium configurations are promising; however, such methods remain relatively unexplored for anion placement. Here, we report the synthesis of LaOI nanocrystals by a non-hydrolytic sol-gel condensation reaction and their transformation into LaOBr, LaOCl, and LaOF nanocrystals along hard–soft acid–base principles using post-synthetic metathesis reactions with ammonium halides. Anion displacement proceeds along halide planes, preserving the tetragonal matlockite structure. Energy-variant X-ray excited optical luminesce signatures of alloyed Tb3+-ions is a sensitive quantum reporter of the preservation of the cation sublattice and hardening of the crystal structure upon anion replacement.
https://ift.tt/3fq6k2j
Well, title's a start. Just curious if the term lattice energy is used outside of something an ionic compound like NaCl.
How about an organic compound that isn't salted, say the freebase of the same alkaloid or a different compound completely like benzophenone or something? Do they have lattice energy?
And a slightly tangential question: Why are alkaloids in the salt form more willing to form crystal structures?
Journal of the American Chemical SocietyDOI: 10.1021/jacs.0c12545
Wei Zhang, Yucen Li, Chunjing Shi, Ruijuan Qi, and Ming Hu
https://ift.tt/3niAh6p
My textbook (Arthur Beiser Intro to Modern Physics) states that "unbound low-energy electrons can travel freely through a crystal since their waves are long relative to the lattice spacing a " in the chapter on solid state physics.
Now I understand that high-energy electrons with wavelengths comparable to the lattice spacing a will undergo diffraction (just like x-rays diffract when they impinge upon a crystal). Hence these electrons will not be able to travel freely through the lattice. Clearly this diffraction will not occur for low-energy electrons with wavelengths much longer than a. But surely these low-energy electrons will still reflect off the lattice planes in the same way that visible light reflects off a crystal (as opposed to x-rays which diffract off the lattice)? The fact that the low energy electrons have wavelengths much longer than the lattice spacing a doesn't seem to indicate that they should be able to travel freely through the lattice because they should still be reflecting off the bragg planes. So why does the author infer that low energy electrons should be able to travel freely through the crystal?
Any help on this issue would be most appreciated!
