Structural distortion of B1B1-structured MnO and FeO

The structural distortion of B1B1-structured MnO and FeO under high pressure is investigated using ab initio methods within GGA and GGA+U approximations. Present calculations indicated that the ordinary density-functional calculation overestimated the structural distortion of MnO and FeO under pressure. When the strong electronic correlations are included in the form of GGA+U, a reasonable description of the structural distortion under high pressure can be obtained. The overestimation of exchange interactions in ordinary DFT calculations may be the most important reason for the overestimation of structural distortion.