For a specific carbon chain, as previous DFT calculations revealed , the difference in length between long and short C-C bonds gradually decreases from both ends of the chain to its center, which is more clearly demonstrated by the BLA diagrams in Fig. . For different carbon chains, with the increase of chain length, the long and short C-C bonds at corresponding positions in the molecule tend to gradually shorten and lengthen, respectively. However, the C-H bond does not change quantitatively with the chain growth, which is also consistent with the previous theoretical reports . Although the regularity of the above two points about BLA seems slight in the carbon chains of finite length currently studied, it is conceivable that when the chain length increases infinitely, the accumulation of these laws is bound to be obvious. It is expected that all the long and short C-C bonds of the infinite length carbon chain may respectively converge to a constant value. From the extrapolation formulas of the C-C bond length in carbon chains H-(C≡C) n -H given by Scemama et al. , it can be inferred that the lengths of long and short C-C bonds in infinitely long carbon chain are about 1.329 and 1.229 Å, respectively.