7.
已知\(ABCD-A_{1}B_{1}C_{1}D_{1}\)为正方体,给出下列四个命题:
\(①(\overrightarrow{A_{1}A}+\overrightarrow{A_{1}D_{1}}+\overrightarrow{A_{1}B_{1}})^{2}=3\overrightarrow{A_{1}B_{1}}^{2}\);
\(②\overrightarrow{A_{1}C}·(\overrightarrow{A_{1}B_{1}}-\overrightarrow{A_{1}A})=0\);
\(③\)向量\(\overrightarrow{AD_{1}}\)与向量\(\overrightarrow{A_{1}B}\)的夹角是\(60^{\circ}\);
\(④\)正方体\(ABCD-A_{1}B_{1}C_{1}D_{1}\)的体积为\(|\overrightarrow{AB}·\overrightarrow{AA_{1}}·\overrightarrow{AD}|.\)
其中正确命题的序号是________.