Structure, electron density and thermal motion of KCuF₃

Ab initiostudy of magnetic interactions inKCuF3andK2Moreira1, Illas2 1999Phys. Rev. B32050View full textAdd to dashboardCite

“…19͒ suggested that the KCuF 3 structure was slightly distorted from the cubic prototypical KNiF 3 one. This interpretation is in agreement with recent x-ray diffraction measurements 20 and with a particular orbital ordering of the magnetic orbitals claimed by Khomskii and Kugel' 21,22 based on the cooperative JahnTeller effect. This fact explained the actual distorted structure of KCuF 3 and also properly predicted that K 2 CuF 4 will exhibit an analogous Jahn-Teller distorted structure with feeble ferromagnetic interactions in the magnetic planes.…”

“…Depending on the stacking of the ab planes along the c axis, KCuF 3 has two ordered polytype structures: twisted, A ͑Fig. 2͒, and untwisted, D. 19,20 In a given sample these two polytype forms usually coexist and preparation of pure phases requires careful synthesis.…”

Computation of correlation-induced atomic displacements and structural transformations in paramagneticKCuF3andLaMnO3

“…24 The latter is characterized by CuF 6 octahedra elongated along the a and b axis and arranged in an antiferro-distortive pattern in the ab plane. 30 At room temperature, there are two different structural polytypes with antiferro (a-type) and ferrolike (d-type) stacking of the ab planes along the c axis. 40 The JT distortion is associated with the particular orbital order in KCuF 3 , in which a single hole alternatingly occupies d x 2 −z 2 and d y 2 −z 2 orbital states, resulting in a tetragonal compression (c < a) of the unit cell.…”

“…In these calculations we have used the experimental room-temperature crystal structure with space group I4/mcm and lattice constants a = 5.855 and c = 7.852Å. 30 The calculations were performed for different values of the JT distortion defined accordingly as…”

“…At room temperature, both compounds have a distorted perovskite structure with a strong cooperative JT distortion. Considering this structural complexity, KCuF 3 has a relatively high (tetragonal) symmetry, 30 where only the cooperative JT distortion of the CuF 6 octahedra is responsible for the deviation from the cubic perovskite symmetry. LaMnO 3 instead crystallizes in a more complex (orthorhombic) structure in which MnO 6 octahedra are simultaneously JT distorted and tilted with respect to the ideal cubic perovskite structure.…”