The reason that it's sigma is if you look at the bonding axis here, is that there is no nodal plane along the bonding axis.
它是sigma键的原因是，因为如果你看键轴，上面是没有节面的。
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By modeling, the formulas for calculating the line peel-off intensity and the plane peel-off intensity were deduced, and the standard to estimate the bonding strength was put forward.