Theory-directed discovery of high-temperature superconductivity in clathrate hydrides at high pressure

Abstract

Main textThe search for room-temperature superconductivity has been one of the great challenges in condensed matter physics ever since the first observation of superconductivity with a critical temperature (Tc) of 4 K in mercury in 1911. In recent years, we have been witness to the successful observation of superconductivity in highly compressed SH3 (Tc = 203 K at 155 GPa) and classes of clathrate hydrides (e.g., CaH6, YH6, YH9, LaH10), with LaH10 holding a record high Tc of 250–260 K at ∼180 GPa among these binary hydrides (Figure 1).1Gao G. Wang L. Li M. et al.Superconducting binary hydrides: theoretical predictions and experimental progresses.Mater. Today Phys. 2021; 21: 100546Google Scholar,2Hilleke K.P. Zurek E. Tuning chemical precompression: theoretical design and crystal chemistry of novel hydrides in the quest for warm and light superconductivity at ambient pressures.J. Appl. Phys. 2022; 131: 070901Google Scholar Each of these experimental studies was guided by theoretical predictions. New experimental work on the Ca-H system has finally confirmed the theoretical calculation that launched this effort, the 2012 prediction of a high-Tc superconductivity in CaH6 above 200 K.1Gao G. Wang L. Li M. et al.Superconducting binary hydrides: theoretical predictions and experimental progresses.Mater. Today Phys. 2021; 21: 100546Google Scholar, 2Hilleke K.P. Zurek E. Tuning chemical precompression: theoretical design and crystal chemistry of novel hydrides in the quest for warm and light superconductivity at ambient pressures.J. Appl. Phys. 2022; 131: 070901Google Scholar, 3Wang H. Tse J.S. Tanaka K. et al.Superconductive sodalite-like clathrate calcium hydride at high pressures.Proc. Natl. Acad. Sci. U S A. 2012; 109: 6463Google ScholarFirst-principles structure-search methods, which require only the chemical composition as input without prior information about the arrangement of atoms, can identify the thermodynamically stable and metastable structures of materials at any pressure and 0 K. Armed with these state-of-the-art methods, several major materials discoveries under pressure have now been documented, one of which is the observation of an anti-Wilson transition:4Ma Y. Eremets M. Oganov A.R. et al.Transparent dense sodium.Nature. 2009; 458: 182Google Scholar the prototypical free-electron metal of sodium transforming to a transparent semiconductor at megabar pressures, in violation of the nearly 1-century old concept that the metallic state is the highest pressure form of materials. Subsequent structure-search simulations led to major discoveries of pressure-stabilized hydrides with Tc approaching room temperature, realizing materials-by-design for this new class of materials.In addition to the advanced structure-search methods, a key role in leading to the discovery of these high-Tc superconducting materials is that the phonon-mediated Bardeen-Cooper-Schrieffer theory describes the high-Tc superconducting properties of these hydrides remarkably well. According to this theory, high critical temperatures may be realized by a large density state at the Fermi level, a high average vibrational frequency, and strong electron-phonon coupling. In this regard, it has long been believed that atomic metallic hydrogen, which was first pointed out by Ashcroft in 1968, would be a very-high-Tc superconductor, as it is predicted to exhibit the above electronic and vibrational properties.1Gao G. Wang L. Li M. et al.Superconducting binary hydrides: theoretical predictions and experimental progresses.Mater. Today Phys. 2021; 21: 100546Google Scholar,2Hilleke K.P. Zurek E. Tuning chemical precompression: theoretical design and crystal chemistry of novel hydrides in the quest for warm and light superconductivity at ambient pressures.J. Appl. Phys. 2022; 131: 070901Google Scholar However, the pressures required to produce atomic metallic hydrogen are estimated to become extremely high (∼500 GPa), which creates a challenge for experimental characterization.An alternative approach was later proposed by Ashcroft in 2004, in which hydrogen-rich materials may exhibit “chemical precompression” that could reduce the onset pressure of metallic hydrogen-like superconductivity by forming dense hydrides.1Gao G. Wang L. Li M. et al.Superconducting binary hydrides: theoretical predictions and experimental progresses.Mater. Today Phys. 2021; 21: 100546Google Scholar,2Hilleke K.P. Zurek E. Tuning chemical precompression: theoretical design and crystal chemistry of novel hydrides in the quest for warm and light superconductivity at ambient pressures.J. Appl. Phys. 2022; 131: 070901Google Scholar The structures of all high-Tc hydrides studied to date can be viewed as various clathrate-like structures. From a Zintl-Klemm description, the metal atoms donate their valence electrons and weaken the H2 molecules in these clathrate-like structures. Thus, the stability of these clathrate hydride structures can be considered to be a balance between the number of electrons available by charge transfer from the metal ions and the size of those metal ions. Electrons are shared to form connected networks of multi-center H … H … H bonds that resemble the bonding environment of atomic metallic hydrogen, and thus electronic properties such as high density of states at Fermi level, together with high characteristic vibrational frequencies and strong electron-phonon coupling.The high superconductivity observed in compressed earth/actinide hydrides has ushered in a new era of superconductivity research, while this distinct type of clathrate metal hydrides was first proposed for CaH6 using the crystal structure analysis by particle swarm optimization (CALYPSO) crystal structure prediction method in 2012.3Wang H. Tse J.S. Tanaka K. et al.Superconductive sodalite-like clathrate calcium hydride at high pressures.Proc. Natl. Acad. Sci. U S A. 2012; 109: 6463Google Scholar Recent laser-heated diamond anvil cell experiments have confirmed this seminal prediction, with a Tc of 215 K at ∼170 GPa.1Gao G. Wang L. Li M. et al.Superconducting binary hydrides: theoretical predictions and experimental progresses.Mater. Today Phys. 2021; 21: 100546Google Scholar X-ray diffraction measurements are consistent with the predicted clathrate structure of CaH6.1Gao G. Wang L. Li M. et al.Superconducting binary hydrides: theoretical predictions and experimental progresses.Mater. Today Phys. 2021; 21: 100546Google Scholar The results demonstrate that high Tc above 200 K is indeed possible in clathrate hydrides formed from the main group, not only lanthanide/actinide, elements. These findings continue to demonstrate the role of structure search methods in this exciting new field.In 2015, a variety of Tc up to 203 K at ∼155 GPa in sulfur hydrides was measured for the first time and exhibited high-Tc above 200 K, thus sparking a flurry of interest in pressure-stabilized hydrides.1Gao G. Wang L. Li M. et al.Superconducting binary hydrides: theoretical predictions and experimental progresses.Mater. Today Phys. 2021; 21: 100546Google Scholar,2Hilleke K.P. Zurek E. Tuning chemical precompression: theoretical design and crystal chemistry of novel hydrides in the quest for warm and light superconductivity at ambient pressures.J. Appl. Phys. 2022; 131: 070901Google Scholar In this experiment, the initial sample of SH2 has long been believed to dissociate into elemental hydrogen and sulfur at sufficiently high pressures. However, a theoretical study Led by Li and Ma in 2014 predicted two stable high-pressure structures, which were theoretically estimated to have the highest Tc of 80 K at megabar pressure.1Gao G. Wang L. Li M. et al.Superconducting binary hydrides: theoretical predictions and experimental progresses.Mater. Today Phys. 2021; 21: 100546Google Scholar,2Hilleke K.P. Zurek E. Tuning chemical precompression: theoretical design and crystal chemistry of novel hydrides in the quest for warm and light superconductivity at ambient pressures.J. Appl. Phys. 2022; 131: 070901Google Scholar Stimulated by this excellent prediction, researchers synthesized two distinct sample was at temperature and measured to exhibit Tc from to K, in with the predicted SH2 The sample was at room temperature and measured to have high-Tc from to 203 K, which was as the of SH2 into high-Tc SH3 and SH3 is a of that has been synthesized at a pressure of GPa and was predicted to be a 200 K at megabar G. Wang L. Li M. et al.Superconducting binary hydrides: theoretical predictions and experimental progresses.Mater. Today Phys. 2021; 21: 100546Google Scholar,2Hilleke K.P. Zurek E. Tuning chemical precompression: theoretical design and crystal chemistry of novel hydrides in the quest for warm and light superconductivity at ambient pressures.J. Appl. Phys. 2022; 131: 070901Google Scholar as a matter of was not and was viewed as a clathrate structure with S in the of the hydrogen Y. Eremets M. Oganov A.R. et al.Transparent dense sodium.Nature. 2009; 458: 182Google Scholar These excellent findings demonstrate that the theoretical work a critical role in the experiments into high-Tc is now a on chemical with of and hydrogen was to have a Tc of K at the composition and structure at the highest critical temperature to be K.P. Zurek E. Tuning chemical precompression: theoretical design and crystal chemistry of novel hydrides in the quest for warm and light superconductivity at ambient pressures.J. Appl. Phys. 2022; 131: 070901Google Scholar is that the of of a can the superconductivity of binary hydrides as for the and the is one can design a with high Tc that is stable at pressures and as a in ambient in one of the key to electron-phonon of the vibrational in of these high-Tc K. Tse J.S. H. for hydrogen-rich at high Scholar are of light such as and which an that the system has a high characteristic The predicted and stability thermodynamically stable at above K.P. Zurek E. Tuning chemical precompression: theoretical design and crystal chemistry of novel hydrides in the quest for warm and light superconductivity at ambient pressures.J. Appl. Phys. 2022; 131: 070901Google Scholar These findings to the of hydrides as room temperature and under pressure as as very-high-Tc materials that are stable at pressures. is to that new classes of high-Tc structures be predicted and synthesized in the this recent in crystal structure prediction methods, and simulations the discovery of new and high-Tc as as a of such as the possible of together with superconductivity in very-high-Tc Main textThe search for room-temperature superconductivity has been one of the great challenges in condensed matter physics ever since the first observation of superconductivity with a critical temperature (Tc) of 4 K in mercury in 1911. In recent years, we have been witness to the successful observation of superconductivity in highly compressed SH3 (Tc = 203 K at 155 GPa) and classes of clathrate hydrides (e.g., CaH6, YH6, YH9, LaH10), with LaH10 holding a record high Tc of 250–260 K at ∼180 GPa among these binary hydrides (Figure 1).1Gao G. Wang L. Li M. et al.Superconducting binary hydrides: theoretical predictions and experimental progresses.Mater. Today Phys. 2021; 21: 100546Google Scholar,2Hilleke K.P. Zurek E. Tuning chemical precompression: theoretical design and crystal chemistry of novel hydrides in the quest for warm and light superconductivity at ambient pressures.J. Appl. Phys. 2022; 131: 070901Google Scholar Each of these experimental studies was guided by theoretical predictions. New experimental work on the Ca-H system has finally confirmed the theoretical calculation that launched this effort, the 2012 prediction of a high-Tc superconductivity in CaH6 above 200 K.1Gao G. Wang L. Li M. et al.Superconducting binary hydrides: theoretical predictions and experimental progresses.Mater. Today Phys. 2021; 21: 100546Google Scholar, 2Hilleke K.P. Zurek E. Tuning chemical precompression: theoretical design and crystal chemistry of novel hydrides in the quest for warm and light superconductivity at ambient pressures.J. Appl. Phys. 2022; 131: 070901Google Scholar, 3Wang H. Tse J.S. Tanaka K. et al.Superconductive sodalite-like clathrate calcium hydride at high pressures.Proc. Natl. Acad. Sci. U S A. 2012; 109: 6463Google ScholarFirst-principles structure-search methods, which require only the chemical composition as input without prior information about the arrangement of atoms, can identify the thermodynamically stable and metastable structures of materials at any pressure and 0 K. Armed with these state-of-the-art methods, several major materials discoveries under pressure have now been documented, one of which is the observation of an anti-Wilson transition:4Ma Y. Eremets M. Oganov A.R. et al.Transparent dense sodium.Nature. 2009; 458: 182Google Scholar the prototypical free-electron metal of sodium transforming to a transparent semiconductor at megabar pressures, in violation of the nearly 1-century old concept that the metallic state is the highest pressure form of materials. Subsequent structure-search simulations led to major discoveries of pressure-stabilized hydrides with Tc approaching room temperature, realizing materials-by-design for this new class of materials.In addition to the advanced structure-search methods, a key role in leading to the discovery of these high-Tc superconducting materials is that the phonon-mediated Bardeen-Cooper-Schrieffer theory describes the high-Tc superconducting properties of these hydrides remarkably well. According to this theory, high critical temperatures may be realized by a large density state at the Fermi level, a high average vibrational frequency, and strong electron-phonon coupling. In this regard, it has long been believed that atomic metallic hydrogen, which was first pointed out by Ashcroft in 1968, would be a very-high-Tc superconductor, as it is predicted to exhibit the above electronic and vibrational properties.1Gao G. Wang L. Li M. et al.Superconducting binary hydrides: theoretical predictions and experimental progresses.Mater. Today Phys. 2021; 21: 100546Google Scholar,2Hilleke K.P. Zurek E. Tuning chemical precompression: theoretical design and crystal chemistry of novel hydrides in the quest for warm and light superconductivity at ambient pressures.J. Appl. Phys. 2022; 131: 070901Google Scholar However, the pressures required to produce atomic metallic hydrogen are estimated to become extremely high (∼500 GPa), which creates a challenge for experimental characterization.An alternative approach was later proposed by Ashcroft in 2004, in which hydrogen-rich materials may exhibit “chemical precompression” that could reduce the onset pressure of metallic hydrogen-like superconductivity by forming dense hydrides.1Gao G. Wang L. Li M. et al.Superconducting binary hydrides: theoretical predictions and experimental progresses.Mater. Today Phys. 2021; 21: 100546Google Scholar,2Hilleke K.P. Zurek E. Tuning chemical precompression: theoretical design and crystal chemistry of novel hydrides in the quest for warm and light superconductivity at ambient pressures.J. Appl. Phys. 2022; 131: 070901Google Scholar The structures of all high-Tc hydrides studied to date can be viewed as various clathrate-like structures. From a Zintl-Klemm description, the metal atoms donate their valence electrons and weaken the H2 molecules in these clathrate-like structures. Thus, the stability of these clathrate hydride structures can be considered to be a balance between the number of electrons available by charge transfer from the metal ions and the size of those metal ions. Electrons are shared to form connected networks of multi-center H … H … H bonds that resemble the bonding environment of atomic metallic hydrogen, and thus electronic properties such as high density of states at Fermi level, together with high characteristic vibrational frequencies and strong electron-phonon coupling.The high superconductivity observed in compressed earth/actinide hydrides has ushered in a new era of superconductivity research, while this distinct type of clathrate metal hydrides was first proposed for CaH6 using the crystal structure analysis by particle swarm optimization (CALYPSO) crystal structure prediction method in 2012.3Wang H. Tse J.S. Tanaka K. et al.Superconductive sodalite-like clathrate calcium hydride at high pressures.Proc. Natl. Acad. Sci. U S A. 2012; 109: 6463Google Scholar Recent laser-heated diamond anvil cell experiments have confirmed this seminal prediction, with a Tc of 215 K at ∼170 GPa.1Gao G. Wang L. Li M. et al.Superconducting binary hydrides: theoretical predictions and experimental progresses.Mater. Today Phys. 2021; 21: 100546Google Scholar X-ray diffraction measurements are consistent with the predicted clathrate structure of CaH6.1Gao G. Wang L. Li M. et al.Superconducting binary hydrides: theoretical predictions and experimental progresses.Mater. Today Phys. 2021; 21: 100546Google Scholar The results demonstrate that high Tc above 200 K is indeed possible in clathrate hydrides formed from the main group, not only lanthanide/actinide, elements. These findings continue to demonstrate the role of structure search methods in this exciting new field.In 2015, a variety of Tc up to 203 K at ∼155 GPa in sulfur hydrides was measured for the first time and exhibited high-Tc above 200 K, thus sparking a flurry of interest in pressure-stabilized hydrides.1Gao G. Wang L. Li M. et al.Superconducting binary hydrides: theoretical predictions and experimental progresses.Mater. Today Phys. 2021; 21: 100546Google Scholar,2Hilleke K.P. Zurek E. Tuning chemical precompression: theoretical design and crystal chemistry of novel hydrides in the quest for warm and light superconductivity at ambient pressures.J. Appl. Phys. 2022; 131: 070901Google Scholar In this experiment, the initial sample of SH2 has long been believed to dissociate into elemental hydrogen and sulfur at sufficiently high pressures. However, a theoretical study Led by Li and Ma in 2014 predicted two stable high-pressure structures, which were theoretically estimated to have the highest Tc of 80 K at megabar pressure.1Gao G. Wang L. Li M. et al.Superconducting binary hydrides: theoretical predictions and experimental progresses.Mater. Today Phys. 2021; 21: 100546Google Scholar,2Hilleke K.P. Zurek E. Tuning chemical precompression: theoretical design and crystal chemistry of novel hydrides in the quest for warm and light superconductivity at ambient pressures.J. Appl. Phys. 2022; 131: 070901Google Scholar Stimulated by this excellent prediction, researchers synthesized two distinct sample was at temperature and measured to exhibit Tc from to K, in with the predicted SH2 The sample was at room temperature and measured to have high-Tc from to 203 K, which was as the of SH2 into high-Tc SH3 and SH3 is a of that has been synthesized at a pressure of GPa and was predicted to be a 200 K at megabar G. Wang L. Li M. et al.Superconducting binary hydrides: theoretical predictions and experimental progresses.Mater. Today Phys. 2021; 21: 100546Google Scholar,2Hilleke K.P. Zurek E. Tuning chemical precompression: theoretical design and crystal chemistry of novel hydrides in the quest for warm and light superconductivity at ambient pressures.J. Appl. Phys. 2022; 131: 070901Google Scholar as a matter of was not and was viewed as a clathrate structure with S in the of the hydrogen Y. Eremets M. Oganov A.R. et al.Transparent dense sodium.Nature. 2009; 458: 182Google Scholar These excellent findings demonstrate that the theoretical work a critical role in the experiments into high-Tc is now a on chemical with of and hydrogen was to have a Tc of K at the composition and structure at the highest critical temperature to be K.P. Zurek E. Tuning chemical precompression: theoretical design and crystal chemistry of novel hydrides in the quest for warm and light superconductivity at ambient pressures.J. Appl. Phys. 2022; 131: 070901Google Scholar is that the of of a can the superconductivity of binary hydrides as for the and the is one can design a with high Tc that is stable at pressures and as a in ambient in one of the key to electron-phonon of the vibrational in of these high-Tc K. Tse J.S. H. for hydrogen-rich at high Scholar are of light such as and which an that the system has a high characteristic The predicted and stability thermodynamically stable at above K.P. Zurek E. Tuning chemical precompression: theoretical design and crystal chemistry of novel hydrides in the quest for warm and light superconductivity at ambient pressures.J. Appl. Phys. 2022; 131: 070901Google Scholar These findings to the of hydrides as room temperature and under pressure as as very-high-Tc materials that are stable at pressures. is to that new classes of high-Tc structures be predicted and synthesized in the this recent in crystal structure prediction methods, and simulations the discovery of new and high-Tc as as a of such as the possible of together with superconductivity in very-high-Tc The search for room-temperature superconductivity has been one of the great challenges in condensed matter physics ever since the first observation of superconductivity with a critical temperature (Tc) of 4 K in mercury in 1911. In recent years, we have been witness to the successful observation of superconductivity in highly compressed SH3 (Tc = 203 K at 155 GPa) and classes of clathrate hydrides (e.g., CaH6, YH6, YH9, LaH10), with LaH10 holding a record high Tc of 250–260 K at ∼180 GPa among these binary hydrides (Figure 1).1Gao G. Wang L. Li M. et al.Superconducting binary hydrides: theoretical predictions and experimental progresses.Mater. Today Phys. 2021; 21: 100546Google Scholar,2Hilleke K.P. Zurek E. Tuning chemical precompression: theoretical design and crystal chemistry of novel hydrides in the quest for warm and light superconductivity at ambient pressures.J. Appl. Phys. 2022; 131: 070901Google Scholar Each of these experimental studies was guided by theoretical predictions. New experimental work on the Ca-H system has finally confirmed the theoretical calculation that launched this effort, the 2012 prediction of a high-Tc superconductivity in CaH6 above 200 K.1Gao G. Wang L. Li M. et al.Superconducting binary hydrides: theoretical predictions and experimental progresses.Mater. Today Phys. 2021; 21: 100546Google Scholar, 2Hilleke K.P. Zurek E. Tuning chemical precompression: theoretical design and crystal chemistry of novel hydrides in the quest for warm and light superconductivity at ambient pressures.J. Appl. Phys. 2022; 131: 070901Google Scholar, 3Wang H. Tse J.S. Tanaka K. et al.Superconductive sodalite-like clathrate calcium hydride at high pressures.Proc. Natl. Acad. Sci. U S A. 2012; 109: 6463Google Scholar structure-search methods, which require only the chemical composition as input without prior information about the arrangement of atoms, can identify the thermodynamically stable and metastable structures of materials at any pressure and 0 K. Armed with these state-of-the-art methods, several major materials discoveries under pressure have now been documented, one of which is the observation of an anti-Wilson transition:4Ma Y. Eremets M. Oganov A.R. et al.Transparent dense sodium.Nature. 2009; 458: 182Google Scholar the prototypical free-electron metal of sodium transforming to a transparent semiconductor at megabar pressures, in violation of the nearly 1-century old concept that the metallic state is the highest pressure form of materials. Subsequent structure-search simulations led to major discoveries of pressure-stabilized hydrides with Tc approaching room temperature, realizing materials-by-design for this new class of materials. In addition to the advanced structure-search methods, a key role in leading to the discovery of these high-Tc superconducting materials is that the phonon-mediated Bardeen-Cooper-Schrieffer theory describes the high-Tc superconducting properties of these hydrides remarkably well. According to this theory, high critical temperatures may be realized by a large density state at the Fermi level, a high average vibrational frequency, and strong electron-phonon coupling. In this regard, it has long been believed that atomic metallic hydrogen, which was first pointed out by Ashcroft in 1968, would be a very-high-Tc superconductor, as it is predicted to exhibit the above electronic and vibrational properties.1Gao G. Wang L. Li M. et al.Superconducting binary hydrides: theoretical predictions and experimental progresses.Mater. Today Phys. 2021; 21: 100546Google Scholar,2Hilleke K.P. Zurek E. Tuning chemical precompression: theoretical design and crystal chemistry of novel hydrides in the quest for warm and light superconductivity at ambient pressures.J. Appl. Phys. 2022; 131: 070901Google Scholar However, the pressures required to produce atomic metallic hydrogen are estimated to become extremely high (∼500 GPa), which creates a challenge for experimental alternative approach was later proposed by Ashcroft in 2004, in which hydrogen-rich materials may exhibit “chemical precompression” that could reduce the onset pressure of metallic hydrogen-like superconductivity by forming dense hydrides.1Gao G. Wang L. Li M. et al.Superconducting binary hydrides: theoretical predictions and experimental progresses.Mater. Today Phys. 2021; 21: 100546Google Scholar,2Hilleke K.P. Zurek E. Tuning chemical precompression: theoretical design and crystal chemistry of novel hydrides in the quest for warm and light superconductivity at ambient pressures.J. Appl. Phys. 2022; 131: 070901Google Scholar The structures of all high-Tc hydrides studied to date can be viewed as various clathrate-like structures. From a Zintl-Klemm description, the metal atoms donate their valence electrons and weaken the H2 molecules in these clathrate-like structures. Thus, the stability of these clathrate hydride structures can be considered to be a balance between the number of electrons available by charge transfer from the metal ions and the size of those metal ions. Electrons are shared to form connected networks of multi-center H … H … H bonds that resemble the bonding environment of atomic metallic hydrogen, and thus electronic properties such as high density of states at Fermi level, together with high characteristic vibrational frequencies and strong electron-phonon coupling. The high superconductivity observed in compressed earth/actinide hydrides has ushered in a new era of superconductivity research, while this distinct type of clathrate metal hydrides was first proposed for CaH6 using the crystal structure analysis by particle swarm optimization (CALYPSO) crystal structure prediction method in 2012.3Wang H. Tse J.S. Tanaka K. et al.Superconductive sodalite-like clathrate calcium hydride at high pressures.Proc. Natl. Acad. Sci. U S A. 2012; 109: 6463Google Scholar Recent laser-heated diamond anvil cell experiments have confirmed this seminal prediction, with a Tc of 215 K at ∼170 GPa.1Gao G. Wang L. Li M. et al.Superconducting binary hydrides: theoretical predictions and experimental progresses.Mater. Today Phys. 2021; 21: 100546Google Scholar X-ray diffraction measurements are consistent with the predicted clathrate structure of CaH6.1Gao G. Wang L. Li M. et al.Superconducting binary hydrides: theoretical predictions and experimental progresses.Mater. Today Phys. 2021; 21: 100546Google Scholar The results demonstrate that high Tc above 200 K is indeed possible in clathrate hydrides formed from the main group, not only lanthanide/actinide, elements. These findings continue to demonstrate the role of structure search methods in this exciting new In 2015, a variety of Tc up to 203 K at ∼155 GPa in sulfur hydrides was measured for the first time and exhibited high-Tc above 200 K, thus sparking a flurry of interest in pressure-stabilized hydrides.1Gao G. Wang L. Li M. et al.Superconducting binary hydrides: theoretical predictions and experimental progresses.Mater. Today Phys. 2021; 21: 100546Google Scholar,2Hilleke K.P. Zurek E. Tuning chemical precompression: theoretical design and crystal chemistry of novel hydrides in the quest for warm and light superconductivity at ambient pressures.J. Appl. Phys. 2022; 131: 070901Google Scholar In this experiment, the initial sample of SH2 has long been believed to dissociate into elemental hydrogen and sulfur at sufficiently high pressures. However, a theoretical study Led by Li and Ma in 2014 predicted two stable high-pressure structures, which were theoretically estimated to have the highest Tc of 80 K at megabar pressure.1Gao G. Wang L. Li M. et al.Superconducting binary hydrides: theoretical predictions and experimental progresses.Mater. Today Phys. 2021; 21: 100546Google Scholar,2Hilleke K.P. Zurek E. Tuning chemical precompression: theoretical design and crystal chemistry of novel hydrides in the quest for warm and light superconductivity at ambient pressures.J. Appl. Phys. 2022; 131: 070901Google Scholar Stimulated by this excellent prediction, researchers synthesized two distinct sample was at temperature and measured to exhibit Tc from to K, in with the predicted SH2 The sample was at room temperature and measured to have high-Tc from to 203 K, which was as the of SH2 into high-Tc SH3 and SH3 is a of that has been synthesized at a pressure of GPa and was predicted to be a 200 K at megabar G. Wang L. Li M. et al.Superconducting binary hydrides: theoretical predictions and experimental progresses.Mater. Today Phys. 2021; 21: 100546Google Scholar,2Hilleke K.P. Zurek E. Tuning chemical precompression: theoretical design and crystal chemistry of novel hydrides in the quest for warm and light superconductivity at ambient pressures.J. Appl. Phys. 2022; 131: 070901Google Scholar as a matter of was not and was viewed as a clathrate structure with S in the of the hydrogen Y. Eremets M. Oganov A.R. et al.Transparent dense sodium.Nature. 2009; 458: 182Google Scholar These excellent findings demonstrate that the theoretical work a critical role in the experiments into high-Tc is now a on chemical with of and hydrogen was to have a Tc of K at the composition and structure at the highest critical temperature to be K.P. Zurek E. Tuning chemical precompression: theoretical design and crystal chemistry of novel hydrides in the quest for warm and light superconductivity at ambient pressures.J. Appl. Phys. 2022; 131: 070901Google Scholar is that the of of a can the superconductivity of binary hydrides as for the and the is one can design a with high Tc that is stable at pressures and as a in ambient in one of the key to electron-phonon of the vibrational in of these high-Tc K. Tse J.S. H. for hydrogen-rich at high Scholar are of light such as and which an that the system has a high characteristic The predicted and stability thermodynamically stable at above K.P. Zurek E. Tuning chemical precompression: theoretical design and crystal chemistry of novel hydrides in the quest for warm and light superconductivity at ambient pressures.J. Appl. Phys. 2022; 131: 070901Google Scholar These findings to the of hydrides as room temperature and under pressure as as very-high-Tc materials that are stable at pressures. is to that new classes of high-Tc structures be predicted and synthesized in the this recent in crystal structure prediction methods, and simulations the discovery of new and high-Tc as as a of such as the possible of together with superconductivity in very-high-Tc Ma for work was by the and of the of and the for the the for and and the of of from the is by an The

Topics & Concepts