CODEN(USA): CRJHA5 Explaining the magnetism of gold

Robson Fernandes De Farias
2017 Chemistry Research Journal   unpublished
In the present work, a computational study is performed in order to clarify the possible magnetic nature of gold. For such purpose, gas phase Au 2 (zero charge) is modelled, in order to calculate its gas phase formation enthalpy. The calculated values were compared with the experimental value obtained by means of Knudsen effusion mass spectrometric studies. Based on the obtained formation enthalpy values for Au 2 , the compound with two unpaired electrons is the most probable one. The
more » ... one. The calculated ionization energy of modelled Au 2 with two unpaired electrons is 8.94 eV and with zero unpaired electrons, 11.42 eV. The difference (11.42-8.94 = 2.48 eV = 239.29 kJmol-1), is in very good agreement with the experimental value of 226.2 ± 0.5 kJmol-1 to the Au-Au bond. So, as expected, in the specie with none unpaired electrons, the two 6s 1 (one of each gold atom) are paired, forming a chemical bond with bond order 1. On the other hand, in Au 2 with two unpaired electrons, the s-d hybridization prevails, because the relativistic contributions. A molecular orbital energy diagram for gas phase Au 2 is proposed, explaining its paramagnetism (and, by extension, the paramagnetism of gold clusters and nanoparticles). Introduction Despite a study about induced paramagnetism on gold [1], bulk gold (Z= 79; electron configuration [xe] 4f 14 5d 10 6s 1) is known to be a typical diamagnetic material. Magnetic properties of gold nanoparticles and clusters have been reported [2]. However, some results are contradictory, and a clear understanding of this phenomenon is still missing. Apparently, as one pass from bulky solid gold to gold nanoparticles or clusters, the unpairing of electrons takes place. In this connection, to model gas phase gold could be a key procedure to clarify the claimed gold magnetism. As shown to PtF 6 [3], thermochemical data can be of paramount importance to a fully understanding of the magnetic properties of inorganic compounds. In the present work, a computational study is performed in order to clarify the possible magnetic nature of gold. For such purpose, gas phase Au 2 (zero charge) is modelled, in order to calculate its gas phase formation enthalpy.
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