末端间矢量

末端间矢量是从聚合物的一个末端指向另一个末端的矢量，定义为

${\displaystyle {\vec {R}}={\vec {R_{N}}}-{\vec {R_{O}}}=\sum _{i=1}^{N}{\vec {r_{i}}}}$

${\displaystyle {\vec {R}}}$是聚合物的末端间矢量

均方末端间矢量定义为

${\displaystyle {\begin{aligned}\langle R^{2}\rangle &=\langle \sum _{i}{\vec {r_{i}}}\cdot \sum _{j}{\vec {r_{j}}}\rangle \\&=\sum _{i}\sum _{j}\langle {\vec {r_{i}}}\cdot {\vec {r_{j}}}\rangle \\&=\sum _{i}\langle {\vec {r_{i}}}\cdot {\vec {r_{i}}}\rangle +2\sum \sum _{i<j}\langle {\vec {r_{i}}}\cdot {\vec {r_{j}}}\rangle \\\end{aligned}}}$