Using a variety of computational approaches, we demonstrate that the energy landscape of low-density silicon (e.g. silicon clathrates) is considerably more complicated than suggested by previous studies and identify several new prospective low-energy silicon allotropes. Many of our new prospective silicon allotropes contain 4-membered rings, previously thought to be incompatible with low-energy...

The binary intermetallic clathrates K8-xSi46 (x = 0.4; 1.2), Rb6.2Si46, Rb11.5Si136 and Cs7.8Si136 were prepared from M₄Si₄ (M = K, Rb, Cs) precursors by spark-plasma route (SPS) and structurally characterized by Rietveld refinement of PXRD data. The clathrate-II phase Rb11.5Si136 was synthesized for the first time. Partial crystallographic site occupancy of the alkali metals, particularly for ...

Anharmonic guest atom oscillation has direct connection to the thermal transport and thermoelectric behavior of type-I Ba8Ga16Sn30 clathrates. This behavior can be observed through several physical properties, with for example the heat capacity providing a measure of the overall excitation level structure. Localized anharmonic excitations also influence the low-temperature resistivity, as we sh...

We report inelastic neutron scattering (INS) measurements on molecular hydrogen deuteride (HD) trapped in binary cubic (sII) and hexagonal (sH) clathrate hydrates, performed at low temperature using two different neutron spectrometers in order to probe both energy and momentum transfer. The INS spectra of binary clathrate samples exhibit a rich structure containing sharp bands arising from both...

The thermal stability of p-type Ba8Ga16Ge30 clathrates grown from gallium flux has been tested by heat treatment in low pressure Ar atmosphere at 400, 600, and 800 °C. Significant gallium loss was observed for all samples during heat treatment. The treatment at 400 °C does not significantly change the sample properties, and the samples remain p-type and comparable to the untreated, as-prepared,...

Structural analysis and thermal conductivity data on Sr8Ga16Ge30 and Eu8Ga16Ge30 crystals are reported. These compounds form in the cubic space group Pm 3̄n with lattice parameters of 10.721~2! and 10.703~2! Å respectively. Single-crystal x-ray diffraction and structural refinement indicate that the randomly distributed Ga and Ge atoms form a tetrahedrally bonded three-dimensional net in whose c...