TY - JOUR
T1 - Electronic structure of Fe-bearing lazulites
AU - Grodzicki, M.
AU - Redhammer, G. J.
AU - Amthauer, G.
AU - Schünemann, V.
AU - Trautwein, A. X.
AU - Velickov, B.
AU - Schmid-Beurmann, P.
PY - 2003/1/1
Y1 - 2003/1/1
N2 - The Fe end-members scorzalite [Fe2+Al2 3+(PO4 2(OH)2] and barbosalite [Fe2+Fe2 3+(PO4 2(OH)2] of the lazulite series have been investigated by Mössbauer and diffuse reflectance spectroscopy, and by electronic structure calculations in the local spin density approximation. The measured quadrupole splitting (ΔEQ = -3.99 mm/s) in scorzalite is in quantitative agreement with the calculated value (ΔEQ = -3.90 mm/s), as well as its temperature dependence. The optical spectrum of barbosalite can be resolved into three peaks at 8985 cm-1, 10980 cm-1, and 14110 cm-1. These positions correlate well with the two calculated spin-allowed d-d transitions at 8824 cm-1 and 11477 cm-1, and with an intervalence charge transfer transition at about 14200 cm-1. The calculated low-temperature magnetic structure of barbosalite is characterized by a strong antiferromagnetic coupling (J = -84.6 cm-1) within the octahedral Fe3+-chains, whereas a weak antiferromagnetic coupling within the trioctahedral subunit cannot be considered as conclusive. The analysis of the charge and spin densities reveals that more than 90% of the covalent part of the iron-ligand bonds arises from the Fe(4s,4p)-electrons. Clusters of at least 95 atoms are required to reproduce the available experimental data with quantitative accuracy.
AB - The Fe end-members scorzalite [Fe2+Al2 3+(PO4 2(OH)2] and barbosalite [Fe2+Fe2 3+(PO4 2(OH)2] of the lazulite series have been investigated by Mössbauer and diffuse reflectance spectroscopy, and by electronic structure calculations in the local spin density approximation. The measured quadrupole splitting (ΔEQ = -3.99 mm/s) in scorzalite is in quantitative agreement with the calculated value (ΔEQ = -3.90 mm/s), as well as its temperature dependence. The optical spectrum of barbosalite can be resolved into three peaks at 8985 cm-1, 10980 cm-1, and 14110 cm-1. These positions correlate well with the two calculated spin-allowed d-d transitions at 8824 cm-1 and 11477 cm-1, and with an intervalence charge transfer transition at about 14200 cm-1. The calculated low-temperature magnetic structure of barbosalite is characterized by a strong antiferromagnetic coupling (J = -84.6 cm-1) within the octahedral Fe3+-chains, whereas a weak antiferromagnetic coupling within the trioctahedral subunit cannot be considered as conclusive. The analysis of the charge and spin densities reveals that more than 90% of the covalent part of the iron-ligand bonds arises from the Fe(4s,4p)-electrons. Clusters of at least 95 atoms are required to reproduce the available experimental data with quantitative accuracy.
UR - http://www.scopus.com/inward/record.url?scp=0038025951&partnerID=8YFLogxK
U2 - 10.2138/am-2003-0401
DO - 10.2138/am-2003-0401
M3 - Journal articles
AN - SCOPUS:0038025951
SN - 0003-004X
VL - 88
SP - 481
EP - 488
JO - American Mineralogist
JF - American Mineralogist
IS - 4
ER -
