Equation Icon  ∑ μj(rj − ri){ 2(β + γ )∑ μl 2 β − 1∑ μk ( ˙ri)2 ( ˙rj)2 ¨ri = -----3----- 1 − ----2---- ---− ----2-- --- + γ -- + (1 + γ) -- j⁄=i rij c l⁄=i ril c k⁄=jrjk c c [ ]2 } ∑ − 2(1-+-γ)˙ri˙rj − -3- (ri −-rj)˙rj + -1-(rj − ri)¨rj + 3-+-4γ- μj¨rj- c2 2c2 rij 2c2 2c2 rij ∑ { } j⁄=i + 1- μj- [r − r ] ⋅ [(2 + 2 γ)˙r − (1 + 2γ)˙r ] (r˙ − ˙r ) + 𝒪 (c−4), (4.2 ) c2 r3ij i j i j i j j⁄=i