pub fn pair_potential(&self, i: usize, j: usize) -> Option<&PairInteraction> {
        let kind_i = self.particles().kind[i];
        let kind_j = self.particles().kind[j];
        return self.interactions.pair((kind_i, kind_j));
    }
/// Get the pair potential acting between the particles at indexes `i` and `j`.
Get the pair potential acting between the particles at indexes `i` and `j`.
Get the pair potential acting between the particles at indexes ` i ` and ` j ` .
pub fn pair_potential(&self, i: usize, j: usize) -> Option<&PairInteraction> {
        let kind_i = self.particles().kind[i];
        let kind_j = self.particles().kind[j];
        return self.interactions.pair((kind_i, kind_j));
    }
pub fn pair_potential ( & self , i : usize , j : usize ) -> Option < & PairInteraction > { let kind_i = self . particles ( ) . kind [ i ] ; let kind_j = self . particles ( ) . kind [ j ] ; return self . interactions . pair ( ( kind_i , kind_j ) ) ; }
Get the pair potential acting between the particles at indexes `i` and `j`.
Get the pair potential acting between the particles at indexes ` i ` and ` j ` .
&self
i
usize
j
usize