Ab initio analysis of elasticity and stability of Fe-P ordered systems Elastic properties of Fe-P ordered system (namely, the bulk modulus, tetragonal and trigonal shear moduli and theoretical strength under isotropic tension) will be computed by means of pseudopotential ab initio computational program code VASP. Various configurations and relative amounts of constituent atoms in cubic cell will be considered. Comparing energetics of those cases, their stability will be assessed and the influence of a relative amount of P in Fe on computed properties will be studied. Magnetic ordering will be taken into account by means of spin-polarization.