What really annoys me is that we have not seen a single reproduction of LK-99 yet.
A lot of the arxiv papers will measure PXRD. Then they will say stuff like "the position of the peaks is almost identical" (https://arxiv.org/pdf/2308.03110.pdf) (emphasis is mine).
Anyone who knows anything about diffraction knows that almost identical means different.
The original paper specified that LK-99 requires a 0.48% contraction of the unit cell volume. if you are off by a small fraction (either from over- or under-doping) the sample is not LK-99. it is something different.
so far all "reproduction" papers have stated that they created the wrong material, then gone on to show that it does not behave as a superconductor.
I'm not saying that LK-99 is definitely a room temperature superconductor, only that I have not seen a single reproduction attempt actually report the same unit cell parameters as reported by the original paper. Thus not a single reproduction attempt has thus far reproduced LK-99.
They hurried and referenced (although only stating that the work is similar) Griffin who published yesterday, so I'm surprised they didn't reference Lai et. al., who also published yesterday with similar conclusions.
But it'll be interesting to see what happens.
It seems that multiple groups are coming to the agreement that this could theoretically be superconducting. So hopefully people can learn to synthesise it.
(we have at least 4 papers now, the two from yesterday, this one and arxiv:2308.00676)
They write that:
"
As shown in Figure 9, the x-ray diffraction spectrum of the
ground powder of the finally sintered product is highly consistent with the x-ray diffraction
spectrum reported by Lee et al.[3] and coincides well with the diffraction pattern of the apatite.
This proves that we have successfully synthesized the modified lead-apatite as Lee et al.[3.4]
"
(First off, you need to pay to the spectrum swear jar. an XRD pattern is a pattern, not a spectrum, it resolves space, not energy.)
But looking at figure 9 shows that the material is not the same.
They are missing a peak at ~17.5 degrees, and have an extra one around 25 degrees.
Further, all the peaks seem to be shifted about the same amount from the LK-99 structure, as the LK-99 is from pure lead-apatite.
This indicates that they have an even smaller unit cell. So if the .5% compression in the original LK-99 paper is correct, there could easily be an overcompression present in this article.
All the XRD pattern tells you is that they produced something wrong, an that it did not superconduct.
It makes it impressive how pure the phase was in the original LK-99 paper.
I will however say that there are some problems with the XRD pattern in the original paper too:
They did not write which energy the XRD was measured at, one would then guess that it is Cu-Ka, but who knows.
Under any circumstances, a peak should not be missing completely from a powder measurement (if it was a pellet, it could be missing due to orientation effects)
A lot of the arxiv papers will measure PXRD. Then they will say stuff like "the position of the peaks is almost identical" (https://arxiv.org/pdf/2308.03110.pdf) (emphasis is mine).
Anyone who knows anything about diffraction knows that almost identical means different.
The original paper specified that LK-99 requires a 0.48% contraction of the unit cell volume. if you are off by a small fraction (either from over- or under-doping) the sample is not LK-99. it is something different.
so far all "reproduction" papers have stated that they created the wrong material, then gone on to show that it does not behave as a superconductor.
I'm not saying that LK-99 is definitely a room temperature superconductor, only that I have not seen a single reproduction attempt actually report the same unit cell parameters as reported by the original paper. Thus not a single reproduction attempt has thus far reproduced LK-99.