The cohesive energy of Iron

The cohesive energy of Fe is a good example of a "spin" system. This system is colinear which means we can consider electrons either polarised as spin up or spin down.

Like before, the cohesive enerfy v is defined as (for a two atom cell).

$E_{coh}(Fe)={\frac {1}{2}}(E_{bulk}-2E_{iso})$

The differnece between this and our silicon example is that here we: a) turn on colinear magnetism.// b) we manually cycle through the spin states setting the differemce between the up and down to an integer, $n$.// c) the lowest energy spin stae is the one we use for the above calculation.

Vasp settings

nspin=2 Nupdown=$n$

Bulk nupdown=1 Etot=-.15545381E+02 nupdown=2 Etot=-.15828724E+02 nupdown=3 Etot=-.16184416E+02 nupdown=4 Etot=-.16498563E+02 nupdown=5 Etot=-.16460255E+02 nupdown=6 Etot=-.15868657E+02

Isolated