LAUSR

Abstract The analysis of quantum electronic pressure (QEP) in magnesium diboride crystals under increasing simulated hydrostatic compression is carried out. The link between the QEP changes and directional compressibility of MgB2 crystal has been revealed. The preferred arrangement of the regions with the QEP maximum positive values and its minimum changes under increasing hydrostatic compression determine the maximal crystal resistance to external stresses along the layers of boron atoms. The difference in the directions of minimal resistance to uniaxial and hydrostatic compression is explained by the features of the regions with different changes of negative QEP values arranged along the Mg-B bonds and B···B interlayer contacts. In this way analysis of quantum electronic pressure reveals the direct link of microscopic and macroscopic fundamental quantities and throws light on aspects of the hitherto unknown nature of the properties of materials.