Setting onsite coupling to zero doesn't remove it

[Lazersmoke]

Sunny.jl/src/System/OnsiteCoupling.jl

Line 144 in 1888468

iszero(op) && return

I use this in parameter sweeps, where set_onsite_coupling!(sys, <zero matrix>, 1) goes after set_onsite_coupling!(sys, +0.1 * Sz^2, 1) and should remove that coupling

[kbarros]

Agreed.