对“Pentadiamond：一种由sp2和sp3原子组成的五边形网络的硬碳同素异形体”一文的评论
Comment on "Pentadiamond: A Hard Carbon Allotrope of a Pentagonal Network of sp2 and sp3 atoms"
摘要：
在最近的一封信中[1] Y。Fujii等人提出了一种新的碳同素异形体，并声称其极高的杨氏模量和剪切模量分别为1691和1113 GPa，超过金刚石的1.5倍和2倍！作者还声称这种碳改性的独特的负平均泊松比为-0.24，体积模量为381 GPa，声速记录值为28.7 km/s。在这里，我们通过两个独立的计算表明，这些值是作为误差的结果而获得的。新的假设的同素异形体实际上具有相当适度的弹性模量，对于具有类似密度的碳结构来说不显著：体积模量为250 GPa，剪切模量为170 GPa，杨氏模量为417 GPa，正泊松比为0.22。
英文摘要：
In a recent Letter [1] Y. Fujii et al. proposed a new carbon allotrope and claimed its extremely high Young's and shear moduli of 1691 and 1113 GPa, respectively, surpassing those of diamond by 1.5 and 2 times! The authors also claimed unique negative averaged Poisson's ratio of -0.24, bulk modulus of 381 GPa and record value of the sound speed 28.7 km/s for this carbon modification. Here we show by two independent computations that these values were obtained as a result of errors. The new hypothetical allotrope has in fact quite moderate elastic moduli, unremarkable for a carbon structure with similar density: bulk modulus of 250 GPa, shear modulus of 170 GPa,Young's modulus of 417 GPa, positive Poisson's ratio of 0.22.
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