材料期刊网

Under various uniaxial stresses, both strains with low symmetry and isotropic strains of crystals take place. The former gives the strain-induced low-symmetry crystal fields and accordingly splittings of levels; the latter gives the isotropic parts of strain-induced crystal fields and accordingly shifts of levels. By using the wavefunctions obtained from the diagonalization of the complete d(3) energy matrix in a regular octahedral field, the relevant matrix elements and accordingly strain-induced splittings and/or shifts of t(2)(3) E-2 and t(2)(3) (4)A(2) for MgO:Cr3+ have been calculated. Their physical origins have been thoroughly analyzed and revealed. It is the admixtures of basic wavefunctions resulted from the spinorbit interaction and/or Coulomb interaction and/or Kramers degeneracy that make strain-induced splittings of levels nonzero. In contrast with this, strain-induced shifts come mainly from the zero-order approximate wavefunctions. It is found that there are nonvanishing matrix elements of operators T(2)xi, T(2)eta and T(2)zeta between wavefunctions with positive M-s and those with negative M-s', which have important effects on strain-induced splittings of levels. The shifts of t(2)(32)E under both hydrostatic pressure and uniaxial pressure have been uniformly calculated. The important results of Y-c, Z(c), P-c, Q(c) and have been evaluated.