Madelung constant sign ambiguity

[Petar Mali]

Madelung constant is define like

$$A=\pm\sum_j\frac{1}{p_{ij}}$$

So I can always say$$A+X=-(A-X)$$ or $$-A=A$$

Can I sometimes problem with this?

 

[olgranpappy]

Madelung constant is define like

$$A=\pm\sum_j\frac{1}{p_{ij}}$$

So I can always say


$$A+X=-(A-X)$$ or $$-A=A$$

Can I sometimes problem with this?

There seems to be a problem... unless you want A=0.