Issue with 18 Implicit_solvation

[physikerwelt]

it is not i*j but the distance between particle i and j
Link to Implicit_solvation, qID 18

[philsMINT]

the macro

for Gold ID 18 - relative property of two particles

DefMath('\partprop{}{}{}', '{#1}_{#2 #3}', omcd => 'wikidata', meaning => 'Q1621273');
does not work properly - what is the problem?