普林斯顿否认LK99超导可能 结论与北大一致

[boss]

[boss]

看来是白激动了

[bluebottle]

有物理知识和良好直觉的就不敢相信这是真的。当然saturn515之类的无知老将啥都相信。老将这个群体基本由无知无耻的垃圾组成。这就是为什么尽管中美关系非常紧张，也没有优秀的人愿意和老将同流合污。凤凰不会和山鸡同伍。

[萧武达]

一作是哪位将军，老中啊

[Caravel]

普林牛逼，连单晶都做出来了

[goFan]

洋人大学定案了，终于放心了

[happens]

(Dated: August 82023)
In a series of recent reports,doped lead apatite(LK-99) has been proposed as a candidate ambient temperature and pressure superconductor.However, from both an experimental and theoretical perspective, these claims are largelyunsubstantiated.To this endour synthesis and subsequent analysis of an LK-99 sample reveals a multiphase material that does not exhibit high-temperature superconductivity. We study the structure of this phase with single-crystal X-ray diffraction(SXRD) and find a structure consistent with doped Pb10(PO4)6(OH)2. However, the material is transparent which rules out a superconducting nature. From ab initio defect formation energy calculations, we find that the material likely hosts OHanions, rather than divalent O2-anions, within the hexagonal channels and that Cu substitution is highly thermodynamically disfavored. Phonon spectra on the equilibrium structures reveal numerous unstable phonon modes.Together,these calculations suggest it is doubtful that Cu enters the structure in meaningful concentrations,despite initial attempts to model LK-99 in this way.However for the sake of completeness we perform ab initio calculations of the topology,quantum geometry, and Wannier function localization in the Cu-dominated fat bands of four separate doped structures. In all cases, we find they are atomically localized by irreps, Wilson loops, and the Fubini-Study metric.It is unlikely that such bands can support strong superfuidity, and instead are susceptible to ferromagnetism(or out-of-plane antiferromagnetism) at low temperatures, which we find in ab initio studies.In sum,PbgCu(PO4)6(OH)2 could more likely be a magnet, rather than an ambient temperature and pressure superconductor.

[happens]

洋人大学定案了，终于放心了

没定，还没搞清楚。

[airglacier001]

当磁铁也可以摆脱依赖土鳖的稀土，还是赢

(Dated: August 82023)
In a series of recent reports,doped lead apatite(LK-99) has been proposed as a candidate ambient temperature and pressure superconductor.However, from both an experimental and theoretical perspective, these claims are largelyunsubstantiated.To this endour synthesis and subsequent analysis of an LK-99 sample reveals a multiphase material that does not exhibit high-temperature superconductivity. We study the structure of this phase with single-crystal X-ray diffraction(SXRD) and find a structure consistent with doped Pb10(PO4)6(OH)2. However, the material is transparent which rules out a superconducting nature. From ab initio defect formation energy calculations, we find that the material likely hosts OHanions, rather than divalent O2-anions, within the hexagonal channels and that Cu substitution is highly thermodynamically disfavored. Phonon spectra on the equilibrium structures reveal numerous unstable phonon modes.Together,these calculations suggest it is doubtful that Cu enters the structure in meaningful concentrations,despite initial attempts to model LK-99 in this way.However for the sake of completeness we perform ab initio calculations of the topology,quantum geometry, and Wannier function localization in the Cu-dominated fat bands of four separate doped structures. In all cases, we find they are atomically localized by irreps, Wilson loops, and the Fubini-Study metric.It is unlikely that such bands can support strong superfuidity, and instead are susceptible to ferromagnetism(or out-of-plane antiferromagnetism) at low temperatures, which we find in ab initio studies.In sum,PbgCu(PO4)6(OH)2 could more likely be a magnet, rather than an ambient temperature and pressure superconductor.

[萧武达]

普林牛逼，连单晶都做出来了

那是真牛逼，这东西可以做出单晶？
读错了吧，是用单晶X-ray分析方法

虽然是普林斯顿，书还是觉得这个叙述的逻辑有问题

We study the structure of this phase with single-crystal X-ray diffraction(SXRD) and find a structure consistent with doped Pb10(PO4)6(OH)2. However, the material is transparent which rules out a superconducting nature.
我们用单晶X射线衍射（SXRD）研究了该相的结构，发现其结构与掺杂的Pb10（PO4）6（OH）2一致。然而，这种材料是透明的，这排除了超导性质。

逻辑上成立吗？

In sum, PbgCu(PO4)6(OH)2 could more likely be a magnet, rather than an ambient temperature and pressure superconductor.
和这东西 Pb10-xCux(PO4)6O 等价？
俺是外行不太懂啊

[Caravel]

那是真牛逼，这东西可以做出单晶？
读错了吧，是用单晶X-ray分析方法

虽然是普林斯顿，书还是觉得这个叙述的逻辑有问题

We study the structure of this phase with single-crystal X-ray diffraction(SXRD) and find a structure consistent with doped Pb10(PO4)6(OH)2. However, the material is transparent which rules out a superconducting nature.
我们用单晶X射线衍射（SXRD）研究了该相的结构，发现其结构与掺杂的Pb10（PO4）6（OH）2一致。然而，这种材料是透明的，这排除了超导性质。

逻辑上成立吗？

成立啊。

没有单晶样品怎么做SXRD？超导体内部排斥磁场，电磁波没法传播，所以超导体都是不透明的。通过这一点排除了是超导体。

[萧武达]

成立啊。

没有单晶样品怎么做SXRD？超导体内部排斥磁场，电磁波没法传播，所以超导体都是不透明的。通过这一点排除了是超导体。

问题是透明的那个不是 Pb10-xCux(PO4)6O LK-99啊，只是结构类似
LK-99就一陶瓷，结构类似的陶瓷多了
如果它吧 Pb10-xCux(PO4)6O 做成了单晶，倒也是奇功一件，炼丹练出单晶，不亚于常温常压超导的突破吧

[萧武达]

钇钡铜氧，或称钇钡铜氧化物、YBCO，是化学式为YBa2Cu3O7的化合物。它是著名的高温超导体，属于第二类超导体，并且是第一个制得转变温度在液氮沸点以上的材料。

历史
在发现超导性后的第75年，在苏黎世IBM工作的约翰内斯·贝德诺尔茨和卡尔·米勒发现特定的半导体氧化物可以在低于35K的温度下显示出超导性，特别是镧钡铜氧化物，一种缺氧钙钛矿型的潜在材料。
在此基础上，1987年，亨茨维尔亚拉巴马大学的吴茂昆及其研究生（Ashburn和Torng），与休斯顿大学的朱经武和他的学生共同发现了钇钡铜氧，也因此引发了对新高温超导材料的研究热潮。
YBCO是首个超导温度在77K以上的材料，也就是说它的转变温度高于液氮的沸点，用相对便宜的液氮就可以冷却。之前发现的超导体都必须用液氦或液氢冷却（Tb = 20.28 K）。

合成
YBCO最早是通过在1000-1300K加热金属碳酸盐混合物制备的。
4BaCO3 + Y2(CO3)3 + 6 CuCO3 → 2 YBa2Cu3O{7-x} + 13 CO2 + (3+x)O2
现在YBCO的制取以相应的硝酸盐和氧化物为原料。
YBa2Cu3O{7-x}的超导性质与x值（氧含量）很有关系，只有满足0≤x≤0.5的材料在Tc温度下有超导性，当x~0时其转变温度最高，为95K。
除了氧的计量比外，YBCO的性质也由结晶方式决定。在烧结YBCO时必须小心，因为YBCO是晶体材料，只有小心控制退火和淬火的温度和速度，校准晶界，才可以使其超导性达到最佳。
吴茂昆和同事提出了其他合成YBCO的方法，比如化学气相沉积（CVD）[2][3]、溶胶-凝胶[4]以及气溶胶法[5]。这些方法在烧结时仍然需要小心。

结构

YBCO结构
YBCO为钙钛矿缺陷型层状结构，含有CuO-CuO2-CuO2-CuO交替的层，CuO2层可以有变形和皱褶。[2] 钇原子存在于CuO2和CuO2层中，BaO层则在CuO与CuO2两层之间。

当YBa2Cu3O7中氧原子计量小于7时，根据具体数值的不同，这些非计量化合物结构可以有差异，可以化学式中的δ来表示。
\delta = 1时为四方结构，CuO层（Cu(1)）的O(1)为空，不显示超导性。略微增加氧的含量会增加O(1)的占有率。δ< 0.65时b轴形成Cu-O链，结构变为正交，晶格参数分别为a=3.82、b=3.89及其c=11.68Å。当δ ~0.07时超导性最佳，O(1)中只有少数几个为空。

有证据显示，当其它原子取代Cu和Ba[来源请求]时，超导性发生在Cu(2)O层，Cu(1)O(1)链只用作储存电荷（charge reservoirs）。然而镨取代钇后形成化合物的超导性与此相矛盾。

钇钡铜氧的超导长度规表现出各向异性，穿透深度lambda_{ab} ≈150nm，lambda_{c}≈800nm
相干长度xi_{ab} ≈2nm，xi_{c}≈0.4nm
虽然a-b平面的相干长度是c轴的6倍之多，但与传统的超导体，如铌（xi≈40nm）相比仍显得较小。这意味着其超导态易受到界面或晶胞缺陷的影响，因此对制作YBCO时的仪器要求增高，并且YBCO对潮湿环境相当敏感。

[CanGuanGong]

还是得洋大人拍板，强国只能跟在屁股后说好香！

[Mountainlion]

非要给普林贴金。
第一，最后的作者都不是普林的

[萧武达]

成立啊。

没有单晶样品怎么做SXRD？超导体内部排斥磁场，电磁波没法传播，所以超导体都是不透明的。通过这一点排除了是超导体。

并不能这样说吧
1）单晶x-ray分析方法可以分析任何材料，不必一定要单晶才可以
2） 钻石，石墨和石墨烯都是碳 ，无论是外观，还是物理特性都大不相同，不光是透明和不透明的差别

[╭∩╮（￣▽￣）╭∩╮]

niu!