<i>Ab initio</i>study revealing a layered structure in hydrogen-rich KH<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>6</mml:mn></mml:msub></mml:math>under high pressure

Zhou, Dawei; Jin, Xilian; Meng, Xing; Bao, Gang; Ma, Yanming; Liu, Bingbing; Cui, Tian

doi:10.1103/physrevb.86.014118

Cited by 88 publications

(58 citation statements)

References 28 publications

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“…In what follows, such a decrease is also observed in the terms of the superconducting transition temperature calculated by using the relation: ∆ m=1 (T C ) = 0, which gives the T C values equal to 72.91 K, 70.73 K, and 55.50 K at 166 GPa, 230 GPa, and 300 GPa, respectively. We also note, that this decreasing behavior of T C is slightly more evident in the case of our results then in the predictions presented in [9], which based on the McMillan formula [16]. Furthermore, results presented in [9] show that for higher electron-phonon coupling constants McMillan formula underestimate the T C values in KH 6 , whereas in the case when λ is close to the weak-coupling limit (λ < 0.3 [17]) the overestimation can be noticed.…”

Section: Numerical Resultssupporting

confidence: 83%

“…We also note, that this decreasing behavior of T C is slightly more evident in the case of our results then in the predictions presented in [9], which based on the McMillan formula [16]. Furthermore, results presented in [9] show that for higher electron-phonon coupling constants McMillan formula underestimate the T C values in KH 6 , whereas in the case when λ is close to the weak-coupling limit (λ < 0.3 [17]) the overestimation can be noticed. This is due to the fact that BCS theory omits the strong-coupling effects, which are present in the Eliashberg theory.…”

Section: Numerical Resultssupporting

confidence: 83%

“…This theoretical model allows us to provide the quantitative estimations of all of the most important thermodynamic properties of the superconducting phase such as critical temperature, band gap at the Fermi level, specific heat, thermodynamic critical field, and the electron effective mass. We note that our analysis is based on the isotropic Elishaberg equations, following the character of the Eliashberg function (α 2 F (ω)) presented in [9], and adopted for calculations in the present work.…”

Section: Introductionmentioning

confidence: 99%

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Thermodynamics of the hydrogen dominant potassium hydride superconductor at high pressure

Szczęśniak

Szczȩśniak

2015

Solid State Communications

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In the present paper we report comprehensive analysis of the thermodynamic properties of novel hydrogen dominant potassium hydride superconductor (KH6). Our computations are conducted within the Eliashberg theory which yields quantitative estimations of the most important thermodynamic properties of superconducting phase. In particular, we observe, that together with the increasing pressure all the thermodynamic properties decrease, e.g. TC ∈ 72.91, 55.50 K for p ∈ 166, 300 GPa. It is predicted that such decreasing behavior corresponds to the decreasing hydrogen lattice molecularization with increasing pressure value. Futhermore, by calculating the dimensionless thermodynamic ratios, familiar in the Bardeen-Cooper-Schrieffer theory (BCS), it is proved that KH6 material is a strong-coupling superconductor and cannot be quantitatively described within the BCS theory.

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Section: Numerical Resultssupporting

confidence: 83%

Section: Numerical Resultssupporting

confidence: 83%

Section: Introductionmentioning

confidence: 99%

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Thermodynamics of the hydrogen dominant potassium hydride superconductor at high pressure

Szczęśniak

Szczȩśniak

2015

Solid State Communications

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“…Therefore, building on Ashcroft's proposals, density functional theory (DFT) calculations were carried out to predict the structures of hydrides with stoichiometries that are not stable at atmospheric conditions, in the hopes of uncovering hitherto unknown superconductors [19]. Since then, numerous theoretical studies have been performed that investigate the phase diagrams of hydrogen doped with the electropositive alkali metals or alkaline earth metals [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34], as well as the electronegative element iodine [35,36] under pressure. Experimental work on the hydrides of lithium and sodium confirmed that species with unique stoichiometries such as NaH 3 and NaH 7 can be synthesized in diamond anvil cells, but the phases that have been reported to date do not exhibit superconductivity [21,37].…”

Section: Introductionmentioning

confidence: 99%

Superconductivity in Hydrides Doped with Main Group Elements Under Pressure

Shamp¹,

Zurek²

2017

Novel Superconducting Materials

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A priori crystal structure prediction techniques have been used to explore the phase diagrams of hydrides of main group elements under pressure. A number of novel phases with the chemical formulas MHn, n > 1 and M = Li, Na, K, Rb, Cs; MHn, n > 2 and M= Mg, Ca, Sr, Ba; HnI with n > 1 and PH, PH 2 , PH 3 have been predicted to be stable at pressures achievable in diamond anvil cells. The hydrogenic lattices within these phases display a number of structural motifs including H δ− 2 , H − , H − 3 , as well as one-dimensional and three-dimensional extended structures. A wide range of superconducting critical temperatures, Tcs, are predicted for these hydrides. The mechanism of metallization and the propensity for superconductivity are dependent upon the structural motifs present in these phases, and in particular on their hydrogenic sublattices. Phases that are thermodynamically unstable, but dynamically stable, are accessible experimentally. The observed trends provide insight on how to design hydrides that are superconducting at high temperatures.

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“…The first system explored experimentally was silane (SiH 4 ) [17]. Soon after, many others materials have been explored experimentally [18][19][20][21] and theoretically [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40]. …”

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confidence: 99%

High temperature superconductivity in sulfur and selenium hydrides at high pressure

2016

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Abstract. Due to its low atomic mass, hydrogen is the most promising element to search for hightemperature phononic superconductors. However, metallic phases of hydrogen are only expected at extreme pressures (400 GPa or higher). (2015)], shows that metallization of hydrogen can be reached at significantly lower pressure by inserting it in the matrix of other elements. In this work we investigate the phase diagram and the superconducting properties of the H-S systems by means of minima hopping method for structure prediction and density functional theory for superconductors. We also show that Se-H has a similar phase diagram as its sulfur counterpart as well as high superconducting critical temperature. We predict H3Se to exceed 120 K superconductivity at 100 GPa. We show that both H3Se and H3S, due to the critical temperature and peculiar electronic structure, present rather unusual superconducting properties.Under high pressure conditions, insulating and semiconducting materials tend to become metallic, because, with increasing electronic density, the kinetic energy grows faster than the potential energy. As metallicity is a necessary condition for superconductivity, generally becomes more likely under pressure [1,2]. Wigner and Huntington [3], already in 1935 suggested the possibility of a metallic modification of hydrogen under very high pressures. Ashcroft and Richardson predicted [4,5] hydrogen to become metallic under pressure and also the possibility to be a high temperature superconductor. The high critical temperature (T C ) of hydrogen [6-8] is a consequence of its low atomic mass leading to high energy vibrational modes and in turn to a large phase space available for electronphonon scattering to induce superconductivity [9]. However, the estimated metallization pressure [10,11] is beyond the current experimental capabilities [12][13][14][15]. It was only recently that hydrogen-rich compounds (chemically pre-compressed) started to be explored as a way to decrease the tremendous metallization pressure of pure hydrogen [16]. The first system explored experimentally was silane (SiH 4 ) [17]. Soon after, many others materials have been explored experimentally [18][19][20][21] and theoretically [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40].

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Ab initiostudy revealing a layered structure in hydrogen-rich KH6under high pressure

Cited by 88 publications

References 28 publications

Thermodynamics of the hydrogen dominant potassium hydride superconductor at high pressure

Thermodynamics of the hydrogen dominant potassium hydride superconductor at high pressure

Superconductivity in Hydrides Doped with Main Group Elements Under Pressure

High temperature superconductivity in sulfur and selenium hydrides at high pressure

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