La₂Pd₃Ge₅ and Nd₂Pd₃Ge₅ Compounds: Chemical Bonding and Physical Properties

Abstract

The two La 2 Pd 3 Ge 5 and Nd 2 Pd 3 Ge 5 compounds, crystallizing in the oI 40-U 2 Co 3 Ge 5 crystal structure, were targeted for analysis of their chemical bonding and physical properties. The compounds of interest were obtained by arc melting and characterized by differential thermal analysis, scanning electron microscopy, and X-ray diffraction both on powder and on a single crystal (for the La analogue), to ensure the high quality of the samples and accurate crystallographic data. Chemical bonding was studied by analyzing the electronic structure and effective QTAIM charges of La 2 Pd 3 Ge 5 . A significant charge transfer mainly occurs from La to Pd so that Ge species assume tiny negative charges. This result, together with the -(I)COHP analysis, suggests that, in addition to the expected homopolar Ge bonds within zigzag chains, heteropolar interactions between Ge and the surrounding La and Pd occur with multicenter character. Covalent La–Pd interactions increase the complexity of chemical bonding, which could not be adequately described by the simplified, formally obeyed, Zintl–Klemm scheme. Electric resistivity, specific heat, magnetization, and magnetic susceptibility as a function of temperature indicate for both compounds a metallic-like behavior. For Nd 2 Pd 3 Ge 5 , two low-temperature phase transitions are detected, leading to an antiferromagnetic ground state.

Crystal Structure and Magnetism of Noncentrosymmetric Eu2Pd2Sn

“…The presence of a strong Eu contribution to the occupied states is clear evidence of its incomplete ionization and participation in chemical bonding, which is a quite common feature for ternary RE -tetrelides. 34 − 37 The COHP curves (see the Supporting Information ) and ICOHP values (see Table 3 and the Supporting Information ) show only a few differences that can be highlighted and discussed between Eu 2 Pd 2 Sn and Ca 2 Pd 2 Ge.…”

Room Temperature Charge Density Wave in a Tetragonal Polymorph of Gd2Os3Si5 and Study of Its Origin in the RE2T3X5 (RE = Rare Earth, T = Transition Metal, X = Si, Ge) Series

“…We have compiled a list of 235 materials from the handbook on 2:3:5 materials and other sources, − along with their values of c / a b . Compounds with a monoclinic structure are not included.…”

Much more to explore with an oxidation state of nearly four: Pr valence instability in intermetallic m -Pr 2 Co 3 Ge 5

“…Still, Ge has been determined to participate in strong polar-covalent interactions with alkali metals and La (48). It is possible that the strong lanthanide-transition metal interactions exhibited in the 4d transition metal lanthanide germanide systems (49,50) departs from what is observed for Pr 2 Co 3 Ge 5 because of the lower electronegativities of the 3d transition metals. While the role of the transition metal and tetrel elements in the formation of tetravalent Pr are not presently clear, we can broadly state that further investigations should be focused toward 3d transition metal germanides that likely have electronic instabilities, i.e., structural phase transformations.…”