Quaternary Arsenides ACdGeAs₂ (A = K, Rb) Built of Ethane-Like Ge₂As₆ Units

Abstract

Reactions of the elements at high temperature resulted in the quaternary arsenides KCdGeAs2 (650 °C) and RbCdGeAs2 (600 °C). Single-crystal X-ray diffraction analysis reveals that they adopt a new triclinic structure type (space group P1̅, Pearson symbol aP20, Z = 4; a = 8.0040(18) Å, b = 8.4023(19) Å, c = 8.703(2) Å, α = 71.019(3)°, β = 75.257(3)°, γ = 73.746(3)° for KCdGeAs2; a = 8.2692(13) Å, b = 8.4519(13) Å, c = 8.7349(13) Å, α = 71.163(2)°, β = 75.601(2)°, γ = 73.673(2)° for RbCdGeAs2). Two-dimensional anionic layers [CdGeAs2](-) are separated by A(+) cations and are built from ethane-like Ge2As6 units forming infinite chains connected via three- and four-coordinated Cd atoms. Being Zintl phases, these compounds satisfy charge balance and are expected to be semiconducting, as confirmed by band structure calculations on KCdGeAs2, which reveal a band gap of 0.8 eV. KCdGeAs2 is diamagnetic.

Revealing the optoelectronic and thermoelectric properties of the Zintl quaternary arsenides ACdGeAs2 (A = K, Rb)

“…Our calculated energy band gap for KCdGeAs 2 and RbCdGeAs 2 are 1.183 and 0.944 eV respectively. These values are in good agreement with those reported in the previous (0.80 eV) calculation using the TB-LMTO-ASA approach [1]. From the result of Figs.…”

“…1, Table 1, we report the calculated bond lengths and bond angles which show good agreement with the experimental work [1].…”

“…The quaternary arsenides KCdGeAs 2 and RbCdGeAs 2 adopt a triclinic structure [1], the unit crystal structure is shown in Fig. 1, Table 1, we report the calculated bond lengths and bond angles which show good agreement with the experimental work [1].…”

“…These ternary pnictides have closed-shell configurations for all atoms and match well with Zintl configuration as complete transfer of electron occur from one atom (angel) to other atoms [1]. Also, some complex quaternary pnictides comprising both transition-metal and metalloid components (such as AM 1.5 Tt 0.5 As 2 (A = Na, K, Rb; M = Zn, Cd; Tt = Si, Ge, Sn) can be envisaged [2].…”

“…Nowadays, first principles methods have become the most strong computation approach that offer one of the most powerful tools for carrying out theoretical studies of these properties. For Zintl chalcopyrite ACdGeAs 2 (A = K, Rb), Khatun et al have presented with synthesis and characterization, the calculation of structural properties and electronic structure using the plane-wave pseudo-potential method [1]. Compared to full potential methods the plane-wave pseudo-potential methods are limited in describing correctly the electronic behavior.…”