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New metastable SmSi3−x (x=0–0.05) is obtained by high‐pressure high‐temperature synthesis (9.5 GPa, 870–1270 K). Powder diffraction data refinements reveal that the crystal structure of SmSi3 is isotypic to that of YbSi3 (space group I4/mmm, a=7.23634(5) Å, c=11.0854(1) Å). In the crystal structure, two types of Si2 dumbbells agglomerate into layers, which embed the samarium atoms. At ambient pressure, SmSi3 decomposes exothermally upon heating into Si and SmSi2−x. Single‐crystal structure refinements of a specimen SmSi3−x (x=0.05) reveal considerable electron density, which is not accounted for by the YbSi3‐type model. The additional maxima can be assigned to disorder which affects the samarium positions and induces silicon vacancies. Scanning transmission electron microscopy experiments evidence that the disorder can be attributed to extended defects. Magnetic measurements on SmSi3−x reveal van Vleck paramagnetic behavior and antiferromagnetic ordering at low temperatures. Computations within the local spin density approximation (LSDA and LSDA+U) on the crystal structure of SmSi3 reproduce the antiferromagnetic coupling as the favored long‐range order. Quantum chemical analysis of the chemical bonding in SmSi3 reveals two‐center two‐electron bonds within the Si2 dumbbells plus a total of a little less than four electrons in lone pairs at each silicon atom. [ABSTRACT FROM AUTHOR]

New metastable SmSi3−x (x=0–0.05) is obtained by high‐pressure high‐temperature synthesis (9.5 GPa, 870–1270 K). Powder diffraction data refinements reveal that the crystal structure of SmSi3 is isotypic to that of YbSi3 (space group I4/mmm, a=7.23634(5) Å, c=11.0854(1) Å). In the crystal structure, two types of Si2 dumbbells agglomerate into layers, which embed the samarium atoms. At ambient pressure, SmSi3 decomposes exothermally upon heating into Si and SmSi2−x. Single‐crystal structure refinements of a specimen SmSi3−x (x=0.05) reveal considerable electron density, which is not accounted for by the YbSi3‐type model. The additional maxima can be assigned to disorder which affects the samarium positions and induces silicon vacancies. Scanning transmission electron microscopy experiments evidence that the disorder can be attributed to extended defects. Magnetic measurements on SmSi3−x reveal van Vleck paramagnetic behavior and antiferromagnetic ordering at low temperatures. Computations within the local spin density approximation (LSDA and LSDA+U) on the crystal structure of SmSi3 reproduce the antiferromagnetic coupling as the favored long‐range order. Quantum chemical analysis of the chemical bonding in SmSi3 reveals two‐center two‐electron bonds within the Si2 dumbbells plus a total of a little less than four electrons in lone pairs at each silicon atom. [ABSTRACT FROM AUTHOR]

The new metastable binary rare‐earth metal trisilicides RESi3 (RE=Tb, Dy, Er, and Tm) are obtained by high‐pressure high‐temperature synthesis (9.5 GPa, 823–923 K). Powder diffraction data refinements reveal that their crystal structure is isotypic to that of YbSi3, and the values of cell parameters and cell volumes decrease from Tb to Tm. Magnetic measurements on the compounds indicate Curie‐Weiss paramagnetic behavior and antiferromagnetic ordering at low temperatures. The values for TN follow a de Gennes scaling pointing towards Ruderman‐Kittel‐Kasuya‐Yosida (RKKY) interaction. Upon heating at ambient pressure, the RESi3 compounds decompose into Si and RESi2‐x. The new high‐pressure phases TbSi3, DySi3, ErSi3 and TmSi3 adopt atomic arrangements in which two‐dimensional building units of silicon are separated by rare‐earth metal atoms. The silicon environment with five short Si‐Si contacts in connection with the formal charge Si− is incompatible with the classical 8‐N rule. This is confirmed by earlier quantum chemical methods evidencing a mixture of two‐atomic Si‐Si bonds and multiatomic interactions involving lone‐pairs located at silicon atoms. Consequently, the rare‐earth metal trisilicides do not belong to the class of electron‐precise Zintl phases, which is consistent with their earlier observed character of covalent metals. This result is in concert with the present study revealing that compounds RESi3 (RE=Gd‐Tm) follow a de Gennes scaling, which is based on a magnetic coupling via conduction electrons. [ABSTRACT FROM AUTHOR]

Despite the formally larger electron supply that can be provided by a gadolinium atom in comparison with atoms like the alkaline-earth metals, the charge transfer in GdSi SB 3 sb is essentially smaller owing to the smaller electronegativity difference between the metal and silicon atoms. Despite the higher potential oxidation state of Gd in comparison with Ca, the effective charge transfer is smaller, which is in fact in agreement with the smaller electronegativity difference between Gd and Si in comparison to that between Ca and Si. Keywords: chemical bonding; gadolinium; Gdf7electronic state; high-pressure synthesis; silicon EN chemical bonding gadolinium Gdf7electronic state high-pressure synthesis silicon 323 329 7 05/13/22 20220501 NES 220501 Dedicated to Professor Christian Näther on the occasion of his 60th birthday. The crystal structure contains layers of interconnected anionic Si-Si dumbbells separated by gadolinium cations. [Extracted from the article]