cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.24435/materialscloud:vp-ms
title: Efficient Kr/Xe separation from triangular g-C3N4 nanopores: density-functional theory calculations benchmarked with random phase approximation

description: Poly(triazine imide) or PTI is a promising material for molecular sieving membranes, thanks to its atom-thick ordered lattice with an extremely high density (1.6 × 10^14 pores/cm2) of triangular-shaped nanopores of ~0.34 nm diameter. Here, we investigate the application of PTI nanopores in the purification of Kr from Xe to reduce the storage volume of the mixture of 85Kr/Xe. Using van-der-Waals density-functional theory (vdW-DFT) calculations, benchmarked against the random phase approximation (RPA), we calculate the potential energy profiles for Kr and Xe across the nanopores. For each gas, starting from the RPA potential-energy profile, the force-field parameters to be used in the classical molecular dynamics framework are trained to calculate the Helmholtz free energy barrier as a function of temperature, and therefore, the corresponding entropic loss. Overall, due to the much higher activation energy from the adsorbed state in Xe (17.61 and 42.10 kJ/mole for Kr and Xe, respectively), a large Kr/Xe separation selectivity is postulated from the PTI membrane. Furthermore, the combination of atom-thick PTI lattice and high pore density leads to extremely large yet selective permeances for Kr. For example, Kr permeance of 1000 gas permeation units (GPU) accompanying a large Kr/Xe selectivity (>10000) is calculated at 25 °C, significantly better than the state-of-the-art membranes for Kr/Xe separation, making PTI-based membranes a leading candidate to process the hazardous waste of 85Kr/Xe mixture.
DOI: 10.24435/materialscloud:c8-kc
title: Efficient Kr/Xe separation from triangular g-C3N4 nanopores: density-functional theory calculations benchmarked with random phase approximation

description: Poly(triazine imide) or PTI is a promising material for molecular sieving membranes, thanks to its atom-thick ordered lattice with an extremely high density (1.6 × 10^14 pores/cm2) of triangular-shaped nanopores of ~0.34 nm diameter. Here, we investigate the application of PTI nanopores in the purification of Kr from Xe to reduce the storage volume of the mixture of 85Kr/Xe. Using van-der-Waals density-functional theory (vdW-DFT) calculations, benchmarked against the random phase approximation (RPA), we calculate the potential energy profiles for Kr and Xe across the nanopores. For each gas, starting from the RPA potential-energy profile, the force-field parameters to be used in the classical molecular dynamics framework are trained to calculate the Helmholtz free energy barrier as a function of temperature, and therefore, the corresponding entropic loss. Overall, due to the much higher activation energy from the adsorbed state in Xe (17.61 and 42.10 kJ/mole for Kr and Xe, respectively), a large Kr/Xe separation selectivity is postulated from the PTI membrane. Furthermore, the combination of atom-thick PTI lattice and high pore density leads to extremely large yet selective permeances for Kr. For example, Kr permeance of 1000 gas permeation units (GPU) accompanying a large Kr/Xe selectivity (>10000) is calculated at 25 °C, significantly better than the state-of-the-art membranes for Kr/Xe separation, making PTI-based membranes a leading candidate to process the hazardous waste of 85Kr/Xe mixture.
DOI: 10.24435/materialscloud:ay-bf
title: Linear and quadratic magnetoresistance in the semimetal SiP2

description: Multiple mechanisms for extremely large magnetoresistance (XMR) found in many topologically nontrivial/trivial semimetals have been theoretically proposed, but experimentally it is unclear which mechanism is responsible in a particular sample. In this paper, by the combination of band structure calculations, numerical simulations of magnetoresistance (MR), Hall resistivity, and de Haas-van Alphen (dHvA) oscillation measurements, we studied the MR anisotropy of SiP2 which is verified to be a topologically trivial, incomplete compensation semimetal. It was found that as magnetic field H is applied along the a-axis, the MR exhibits an unsaturated nearly linear H dependence, which was argued to arise from incomplete carriers compensation. For the H // [101] orientation, an unsaturated nearly quadratic H dependence of MR up to 5.88 × 10^4%(at 1.8 K, 31.2 T) and field-induced up-turn behavior in resistivity were observed, which was suggested due to the existence of hole open orbits extending along the kx direction. Good agreement of the experimental results with the simulations based on the calculated Fermi surface (FS) indicates that the topology of FS plays an important role in its MR.
DOI: 10.24435/materialscloud:sa-s1
title: Linear and quadratic magnetoresistance in the semimetal SiP2

description: Multiple mechanisms for extremely large magnetoresistance (XMR) found in many topologically nontrivial/trivial semimetals have been theoretically proposed, but experimentally it is unclear which mechanism is responsible in a particular sample. In this paper, by the combination of band structure calculations, numerical simulations of magnetoresistance (MR), Hall resistivity, and de Haas-van Alphen (dHvA) oscillation measurements, we studied the MR anisotropy of SiP2 which is verified to be a topologically trivial, incomplete compensation semimetal. It was found that as magnetic field H is applied along the a-axis, the MR exhibits an unsaturated nearly linear H dependence, which was argued to arise from incomplete carriers compensation. For the H // [101] orientation, an unsaturated nearly quadratic H dependence of MR up to 5.88 × 10^4%(at 1.8 K, 31.2 T) and field-induced up-turn behavior in resistivity were observed, which was suggested due to the existence of hole open orbits extending along the kx direction. Good agreement of the experimental results with the simulations based on the calculated Fermi surface (FS) indicates that the topology of FS plays an important role in its MR.
DOI: 10.24435/materialscloud:c0-q1
title: Detecting electron-phonon coupling during photoinduced phase transition

description: This record contains the data supporting our recent findings on electron-phonon coupling during photoinduced phase transition.
We measure mode- and band-selective electron-phonon couplings during the photoinduced insulator-to-metal phase transition in Ta2NiSe5 (TNS) by frequency-domain angle-resolved photoemission spectroscopy (FDARPES).
FDARPES gives us rich information about which band more couples which phonon mode by seeing frequency components of time-resolved angle-resolved photoemission spectra. 
The experiments indicate 2 THz and 3 THz phonon modes associated with the metallic and semiconducting phases. 
To get a more atomistic picture of the oscillation, we perform phonon-mode calculations relying on the density-functional theory (DFT).

The computational scheme itself is very standard that density-functional-perturbation theory (DFPT) with semilocal or local exchange-correlation functionals. 
However, the required computational resources were rather huge, 25,000 core-hour, for a single DFPT with atomic position optimization having 0.1 eV/nm force accuracy for more satisfactory computational parameters. 
Therefore, the data must be worth as a benchmark within DFT-level calculation for TNS.
DOI: 10.24435/materialscloud:mt-ey
title: Pushing the limits of the donor-acceptor copolymer strategy for intramolecular singlet fission

description: Donor–acceptor (D–A) copolymers have shown great potential for intramolecular singlet fission (iSF). Nonetheless, very few design principles exist for optimizing these systems for iSF, with very little knowledge about how to engineer them for this purpose. In recent work, a fundamental trade-off between the main electronic ingredients required for iSF capable D–A coplanar copolymers was revealed. Still, further investigations are needed to understand these limitations and learn how to bypass them. In this work, we propose to induce torsion as an effective way to circumvent the limits of the coplanar approach. We disclose the potential of noncoplanar copolymers with inherently low triplet energies that encompass all the characteristics required for iSF beyond the limiting values associated with fully coplanar systems. Our findings shed some light on the electronic structure aspects of D–A copolymers for iSF and offer a new avenue for the rational design of novel promising candidates.
DOI: 10.24435/materialscloud:w1-88
title: Detecting electron-phonon coupling during photoinduced phase transition

description: This record contains the data supporting our recent findings on electron-phonon coupling during photoinduced phase transition.
We measure mode- and band-selective electron-phonon couplings during the photoinduced insulator-to-metal phase transition in Ta2NiSe5 (TNS) by frequency-domain angle-resolved photoemission spectroscopy (FDARPES).
FDARPES gives us rich information about which band more couples which phonon mode by seeing frequency components of time-resolved angle-resolved photoemission spectra. 
The experiments indicate 2 THz and 3 THz phonon modes associated with the metallic and semiconducting phases. 
To get a more atomistic picture of the oscillation, we perform phonon-mode calculations relying on the density-functional theory (DFT).

The computational scheme itself is very standard that density-functional-perturbation theory (DFPT) with semilocal or local exchange-correlation functionals. 
However, the required computational resources were rather huge, 25,000 core-hour, for a single DFPT with atomic position optimization having 0.1 eV/nm force accuracy for more satisfactory computational parameters. 
Therefore, the data must be worth as a benchmark within DFT-level calculation for TNS.
DOI: 10.24435/materialscloud:4j-yn
title: Pushing the limits of the donor-acceptor copolymer strategy for intramolecular singlet fission

description: Donor–acceptor (D–A) copolymers have shown great potential for intramolecular singlet fission (iSF). Nonetheless, very few design principles exist for optimizing these systems for iSF, with very little knowledge about how to engineer them for this purpose. In recent work, a fundamental trade-off between the main electronic ingredients required for iSF capable D–A coplanar copolymers was revealed. Still, further investigations are needed to understand these limitations and learn how to bypass them. In this work, we propose to induce torsion as an effective way to circumvent the limits of the coplanar approach. We disclose the potential of noncoplanar copolymers with inherently low triplet energies that encompass all the characteristics required for iSF beyond the limiting values associated with fully coplanar systems. Our findings shed some light on the electronic structure aspects of D–A copolymers for iSF and offer a new avenue for the rational design of novel promising candidates.
DOI: 10.24435/materialscloud:k6-6p
title: Electronic structure of water from Koopmans-compliant functionals

description: Obtaining a precise theoretical description of the spectral properties of liquid water poses challenges for both molecular dynamics (MD) and electronic structure methods. The lower computational cost of the Koopmans-compliant functionals with respect to Green's function methods allows the simulations of many MD trajectories, with a description close to the state-of-art quasi-particle self-consistent GW plus vertex corrections method (QSGW + fxc). Thus, we explore water spectral properties when different MD approaches are used, ranging from classical MD to first-principles MD, and including nuclear quantum effects. We have observed that different MD approaches lead to up to 1 eV change in the average band gap; thus, we focused on the band gap dependence with the geometrical properties of a system to explain such spread. We have evaluated the changes in the band gap due to variations in the intramolecular O–H bond distance and HOH angle, as well as the intermolecular hydrogen bond O···O distance and the OHO angles. We have observed that the dominant contribution comes from the O–H bond length; the O···O distance plays a secondary role, and the other geometrical properties do not significantly influence the gap. Furthermore, we analyze the electronic density of states (DOS), where the KIPZ functional shows good agreement with the DOS obtained with state-of-art approaches employing quasi-particle self-consistent GW plus vertex corrections. The O–H bond length also significantly influences the DOS. When nuclear quantum effects are considered, broadening of the peaks driven by the broader distribution of the O–H bond lengths is observed, leading to a closer agreement with the experimental photoemission spectra.
DOI: 10.24435/materialscloud:76-zf
title: Electronic structure of water from Koopmans-compliant functionals

description: Obtaining a precise theoretical description of the spectral properties of liquid water poses challenges for both molecular dynamics (MD) and electronic structure methods. The lower computational cost of the Koopmans-compliant functionals with respect to Green's function methods allows the simulations of many MD trajectories, with a description close to the state-of-art quasi-particle self-consistent GW plus vertex corrections method (QSGW + fxc). Thus, we explore water spectral properties when different MD approaches are used, ranging from classical MD to first-principles MD, and including nuclear quantum effects. We have observed that different MD approaches lead to up to 1 eV change in the average band gap; thus, we focused on the band gap dependence with the geometrical properties of a system to explain such spread. We have evaluated the changes in the band gap due to variations in the intramolecular O–H bond distance and HOH angle, as well as the intermolecular hydrogen bond O···O distance and the OHO angles. We have observed that the dominant contribution comes from the O–H bond length; the O···O distance plays a secondary role, and the other geometrical properties do not significantly influence the gap. Furthermore, we analyze the electronic density of states (DOS), where the KIPZ functional shows good agreement with the DOS obtained with state-of-art approaches employing quasi-particle self-consistent GW plus vertex corrections. The O–H bond length also significantly influences the DOS. When nuclear quantum effects are considered, broadening of the peaks driven by the broader distribution of the O–H bond lengths is observed, leading to a closer agreement with the experimental photoemission spectra.
DOI: 10.24435/materialscloud:dr-9y
title: Electronic structure of water from Koopmans-compliant functionals

description: Obtaining a precise theoretical description of the spectral properties of liquid water poses challenges for both molecular dynamics (MD) and electronic structure methods. The lower computational cost of the Koopmans-compliant functionals with respect to Green's function methods allows the simulations of many MD trajectories, with a description close to the state-of-art quasi-particle self-consistent GW plus vertex corrections method (QSGW + fxc). Thus, we explore water spectral properties when different MD approaches are used, ranging from classical MD to first-principles MD, and including nuclear quantum effects. We have observed that different MD approaches lead to up to 1 eV change in the average band gap; thus, we focused on the band gap dependence with the geometrical properties of a system to explain such spread. We have evaluated the changes in the band gap due to variations in the intramolecular O–H bond distance and HOH angle, as well as the intermolecular hydrogen bond O···O distance and the OHO angles. We have observed that the dominant contribution comes from the O–H bond length; the O···O distance plays a secondary role, and the other geometrical properties do not significantly influence the gap. Furthermore, we analyze the electronic density of states (DOS), where the KIPZ functional shows good agreement with the DOS obtained with state-of-art approaches employing quasi-particle self-consistent GW plus vertex corrections. The O–H bond length also significantly influences the DOS. When nuclear quantum effects are considered, broadening of the peaks driven by the broader distribution of the O–H bond lengths is observed, leading to a closer agreement with the experimental photoemission spectra.
DOI: 10.24435/materialscloud:8w-q6
title: Enhancing sub-bandgap external quantum efficiency by photomultiplication for narrowband organic near-infrared photodetectors

description: Detection of electromagnetic signals for applications such as health, product quality monitoring or astronomy requires highly responsive and wavelength selective devices. Photomultiplication-type organic detectors (PM-OPDs) have shown to achieve high quantum efficiencies mainly in the visible range. Much less research has been focused on realizing near-infrared narrowband PM-OPDs. Here, we demonstrate fully vacuum-processed narrow- and broadband PM‑OPDs. Our devices are based on enhanced hole injection leading to a maximum external quantum efficiency (EQE) of almost 2000% at -10 V for the broadband device. The photomultiplicative effect is also observed in the charge-transfer (CT) state absorption region. By making use of an optical cavity device architecture, we enhance CT absorption and demonstrate a wavelength tunable narrowband PM-OPD with EQEs superior to those of pin‑devices. The presented concept can further improve the performance of state-of-the-art OPDs based on the absorption of CT states, which were so far limited by the low EQE provided by these devices.
DOI: 10.24435/materialscloud:m3-cj
title: Enhancing sub-bandgap external quantum efficiency by photomultiplication for narrowband organic near-infrared photodetectors

description: Detection of electromagnetic signals for applications such as health, product quality monitoring or astronomy requires highly responsive and wavelength selective devices. Photomultiplication-type organic detectors (PM-OPDs) have shown to achieve high quantum efficiencies mainly in the visible range. Much less research has been focused on realizing near-infrared narrowband PM-OPDs. Here, we demonstrate fully vacuum-processed narrow- and broadband PM‑OPDs. Our devices are based on enhanced hole injection leading to a maximum external quantum efficiency (EQE) of almost 2000% at -10 V for the broadband device. The photomultiplicative effect is also observed in the charge-transfer (CT) state absorption region. By making use of an optical cavity device architecture, we enhance CT absorption and demonstrate a wavelength tunable narrowband PM-OPD with EQEs superior to those of pin‑devices. The presented concept can further improve the performance of state-of-the-art OPDs based on the absorption of CT states, which were so far limited by the low EQE provided by these devices.
DOI: 10.24435/materialscloud:21-m1
title: Evaluation of photocatalysts for water splitting through combined analysis of surface coverage and energy-level alignment

description: To examine whether suitable conditions occur for the water splitting reaction at their interfaces with liquid water, we determine the pH-dependent surface coverage for a series of semiconductors, including GaAs, GaP, GaN, CdS, ZnO, SnO2, rutile and anatase TiO2. For this we calculate acidity constants at surface sites through ab initio molecular dynamics simulations and a grand-canonical formulation of adsorbates. The resulting pH values at the point of zero charge show excellent agreement with experiment and thereby support the validity of our approach. By combining information concerning the surface coverage with the alignment of the band edges with respect to the relevant redox levels, we scrutinize the potential of the considered semiconductors as photocatalysts and identify the corresponding optimal pH ranges for hydrogen and oxygen evolution. More specifically, our results indicate that GaN stands out among these semiconductors as the most promising candidate for the overall water splitting, with the potential of further improvement through alloying. With the surface coverage, our computational analysis brings a new descriptor that is at present beyond experimental reach.
DOI: 10.24435/materialscloud:2018.0022/v1
title: Atomic structures of semiconductor surfaces

description: This entry includes the surface structures of some prototypical semiconductors obtained via structural optimizations using the PBE density functional. The structures were initially used for benchmarking ionization potentials calculated with hybrid density functionals and GW approximation.

Seven semiconductor surfaces are provided in the form of Quantum ESPRESSO input: Si(111), C(111),  GaAs(110), GaP(110), ZnSe(110), ZnO(10-10), and TiO2(110).
DOI: 10.24435/materialscloud:bj-ga
title: Evaluation of photocatalysts for water splitting through combined analysis of surface coverage and energy-level alignment

description: To examine whether suitable conditions occur for the water splitting reaction at their interfaces with liquid water, we determine the pH-dependent surface coverage for a series of semiconductors, including GaAs, GaP, GaN, CdS, ZnO, SnO2, rutile and anatase TiO2. For this we calculate acidity constants at surface sites through ab initio molecular dynamics simulations and a grand-canonical formulation of adsorbates. The resulting pH values at the point of zero charge show excellent agreement with experiment and thereby support the validity of our approach. By combining information concerning the surface coverage with the alignment of the band edges with respect to the relevant redox levels, we scrutinize the potential of the considered semiconductors as photocatalysts and identify the corresponding optimal pH ranges for hydrogen and oxygen evolution. More specifically, our results indicate that GaN stands out among these semiconductors as the most promising candidate for the overall water splitting, with the potential of further improvement through alloying. With the surface coverage, our computational analysis brings a new descriptor that is at present beyond experimental reach.
DOI: 10.24435/materialscloud:qb-vk
title: Atomic structures of semiconductor surfaces

description: This entry includes the surface structures of some prototypical semiconductors obtained via structural optimizations using the PBE density functional. The structures were initially used for benchmarking ionization potentials calculated with hybrid density functionals and GW approximation.

Seven semiconductor surfaces are provided in the form of Quantum ESPRESSO input: Si(111), C(111),  GaAs(110), GaP(110), ZnSe(110), ZnO(10-10), and TiO2(110).
DOI: 10.24435/materialscloud:2019.0022/v1
title: Dynamics of the Bulk Hydrated Electron from Many‐Body Wave‐Function Theory

description: Trajectories and spin densities for the bulk hydrated electron at the MP2 level of theory.  The data represent the first ab initio molecular dynamics study of the hydrated electron in the bulk using many-body wave function theory.
DOI: 10.24435/materialscloud:2019.0041/v1
title: Generalized stacking fault energy surfaces for eight face-centered cubic transition metals

description: Density functional theory calculations were used to obtain the generalized stacking fault energy surfaces in eight FCC metals: Ag, Au, Cu, Ir, Ni, Pd, Pt, and Rh. Among them, ferromagnetism was considered only in Ni. Results based on non-magnetic Ni are denoted as Ni-NM.
DOI: 10.24435/materialscloud:x8-6v
title: Dynamics of the Bulk Hydrated Electron from Many‐Body Wave‐Function Theory

description: Trajectories and spin densities for the bulk hydrated electron at the MP2 level of theory.  The data represent the first ab initio molecular dynamics study of the hydrated electron in the bulk using many-body wave function theory.