High‐pressure Raman investigation of the semiconductor antimony oxide

Abstract

The in situ high‐pressure behavior of the semiconductor antimony trioxide (Sb2O3) has been investigated by Raman spectroscopy techniques in a diamond anvil cell up to 20 GPa at room temperature. New peaks in the external lattice mode range emerged at a pressure above 8.6‐15 GPa, suggesting that the structural phase transition occurred. The pressure dependence of Raman frequencies was obtained. The band at 139 cm‐1 (assigned to group mode) has a pressure dependence of ‐0.475 cm‐1/GPa and reveals significant softening at high pressure. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Constraints on a special running vacuum model

“…which leads to H 2 = H 2 0 β/(1 − α), pointing out that the existence of the de-Sitter space appears only if β/(1−α) > 0. As we have discussed [20,21], α ∼ 1 gives us a large abundance of the dark energy density in the early universe, so that the observations require the value of α to be small. On the other hand, the negative value of α induces ρ Λ < 0 at a high z, which should be avoided.…”

“…In order to resolve the "coincidence" problem, people have proposed various models to improve the cosmological constant of Λ in the Einstein's equation, such as the running vacuum models (RVMs) [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]. In this kind of the models, Λ, instead of being a constant, is a function of the Hubble parameter H, and decays to matter and radiation [8].…”

“…In this kind of the models, Λ, instead of being a constant, is a function of the Hubble parameter H, and decays to matter and radiation [8]. It has been shown that the RVMs are suitable in describing the cosmological evolutions on both background and linear perturbation levels in the literature [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33]. In these studies, the Hubble parameter H has been used to compose many forms of Λ = A n H 2n with a nonnegative integer n, where A n is a mass dimension 2(1 − n) constant.…”

“…Naively, it is expected that the values of α and β should be close to zero in order to fit the current cosmological observations. However, in some of the RVMs, the model parameters have been shown to be non-zero and sizable [15][16][17][18][19][20][21]. It is interesting to explore if our special form of the RVMs also has this peculiar feature.…”

Structural and vibrational study of cubic Sb2O3under high pressure

“…In particular, there are studies of As 2 O 3 , 13,14 Bi 2 O 3 , 15,16 and β-Sb 2 O 3 . 17 These works show that while arsenolite and monoclinic α-Bi 2 O 3 undergo a crystalline-to-amorphous transition above 15 and 20 GPa, respectively, claudetite (orthorhombic As 2 O 3 ) remains crystalline to 40 GPa, and a solid-solid phase transition seems to be present near 8 GPa in valentinite. These studies have shown the complex nature of the phase transitions in these sesquioxides and the need to study the pressure-induced phase transitions in other polymorphic phases of these compounds in order to better understand their similarities and differences with respect to other sesquioxides.…”