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Magnetic interactions and electronic structure of uvarovite and andradite garnets. An ab initio all‐electron simulation with the CRYSTAL06 program
Author(s) -
Meyer A.,
Pascale F.,
ZicovichWilson C. M.,
Dovesi R.
Publication year - 2010
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.22302
Subject(s) - andradite , superexchange , chemistry , ab initio , density functional theory , electronic structure , condensed matter physics , mulliken population analysis , ground state , ab initio quantum chemistry methods , antiferromagnetism , computational chemistry , physics , atomic physics , materials science , quartz , organic chemistry , skarn , fluid inclusions , molecule , composite material
The ground‐state electronic structure of a number of magnetic phases of the garnets andradite (Ca 3 Fe 2 Si 3 O 12 ) and uvarovite (Ca 3 Cr 2 Si 3 O 12 ) has been investigated at the density functional theory level of approximation using the periodic ab initio code CRYSTAL. An all‐electron Gaussian‐type basis has been used in conjunction with the B3LYP hybrid functional. The exchange coupling constants between the first ( J 1 a and J 1 b differentiating the two nonidentical sites), second ( J 2 ), and third ( J 3 ) nearest neighbors have been evaluated and are found to be in good agreement with the experimental data that is available for andradite. As a consequence of both the different J 1 a to J 1 b ratio and the opposite sign of J 2 in the two minerals, different antiferromagnetic (AF) ground states are found for uvarovite and andradite, which is in agreement with experimental observation. Strong support for the additivity and transferability of the J constants is provided by calculations in which Cr and Fe ions are embedded in the related grossular structure. The mechanism for the stabilization of the AF states is discussed within the Anderson theory of superexchange; the kinetic energy gain in the AF states is calculated, and the spin density maps and profiles are examined. Density of states, charge density maps, and Mulliken population data complete the analysis of the electronic structure. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010