HPPXRD was used to obtain B for all compounds (Table ). Given the expected subtle differences in the material's pressure response, we have used a custom-built HPPXRD setup to collect HPPXRD data with finely spaced pressure points, step size of Δp = 0.02 GPa, up to a maximum pressure of pmax. = 0.4 GPa (Fig. ) equation of state to the V(p) data. For a better comparison with literature data, both 2 nd and 3 rd order B-M equation of state fits were performed using EOSFit, see SI for the results and all fits of the V(p) and F(f) plots (Fig. ). Similar results were obtained by using PASCal (Table ). Only fits using 2 nd order B-M equation of state show standard errors in fitted B comparable to those observed for the standard material Ni(dmgH)2 (dmgH -= dimethylglyoximate), 𝜎B = ±0.09 GPa. Much larger uncertainties for a 3 rd order B-M fit suggest overparametrisation, see SI (S-66).