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At least 919 records · Page 51
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Measuring Intermolecular Excited State Geometry for Favorable Singlet Fission in Tetracene

Singlet fission (SF) is the process of converting an excited singlet to a pair of excited triplets. Harvesting two charges from a single photon has the potential to increase photovoltaic device efficiencies. Acenes, such as tetracene and pentacene, are model molecules for studying SF. Despite SF being an endoergic process for tetracene and exoergic for pentacene, both acenes exhibit near unity SF quantum efficiencies, raising questions about how tetracene can overcome the energy barrier. Here, we use recently developed instrumentation to measure inelastic neutron scattering (INS) while optically exciting the model molecules using two different excitation energies. The spectroscopic results reveal intermolecular structural relaxation due to the presence of a triplet excited state. Here, the structural dynamics of the combined excited state molecule and surrounding tetracene molecules are further studied using time-dependent density functional theory (TD-DFT), which shows that the singlet and triplet levels shift due to the excited state geometry, reducing the uphill energy barrier for SF to within kT.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Simulation of supersonic molecular beam injection fueling into H-mode plasmas on EAST using BOUT++

Transport dynamic 2D simulations for supersonic molecular beam injection (SMBI) fueling into H-mode deuterium plasmas on the Experimental Advanced Superconducting Tokamak (EAST) is first simulated using a seven-field two-fluid model in the BOUT++ framework. The SMB is assumed to be injected into plasma from the midplane at the low field side with a fixed width and constant molecular flux. The different densities and injection velocities of SMBI are investigated within the upper single-null geometry of EAST. The simulations indicate that the SMBI has a self-shielding effect on molecules' inward transport into the plasma, and the deposition of SMBI leads to a large increase in plasma density and decrease in plasma temperature. There is a velocity threshold for SMB penetrating the pedestal and depositing at the top of density pedestal. However, the deposition point would be back toward the plasma boundary after SMB arriving at the deepest penetration position. Comparing the different molecular injection velocities and densities, the outcomes demonstrate that the depth of deposition is closely related to the injection velocity rather than the molecular density. The simulated results show good agreement with the EAST experiments by comparing the electron density profiles obtained by simulation and experiment, respectively. These results will be helpful for guiding future experiments, as well as the design of the SMBI system.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2026

Consistent inclusion of triple substitutions within a coupled cluster based static quantum embedding theory

We have previously proposed the MPCC static embedding framework for quantum chemistry that self-consistently couples a high-level coupled cluster (CC) treatment of the fragment (active region) with a lower level, Møller–Plesset perturbation treatment of the environment. Our initial implementation was limited to single and double (SD) substitutions, with CCSD for the fragment and first-order perturbative SD amplitudes for the environment. Here, we extend the MPCC embedding treatment to triple substitutions, which is essential for achieving chemical accuracy in energy differences. To this end, we employ a CCSDT solver for the fragment subsystem. For the environment subsystem, we construct a perturbative estimate of the triples amplitudes, explicitly accounting for feedback from all fragment amplitudes. The resulting approach is denoted MPCCSDT(pt). We further introduce a more complete formulation in which feedback from the environment amplitudes to the fragment amplitudes is also included. This scheme involves an iterative treatment of the environment triples amplitudes and is denoted MPCCSDT(it). In addition, we assess the accuracy of the previously proposed low-level method by introducing a modified low-level approach that incorporates a lowest-order treatment of selected long-range effects, including spin fluctuations and charge polarization. All resulting approaches may be viewed as post-CCSD(T) methods. We therefore consider test cases for which CCSD(T) exhibits substantial deviations from CCSDT. These include (i) single- and triple-bond stretching in F 2 and N 2 , (ii) bond dissociation energies of selected molecules from the W4-11 dataset, and (iii) total atomization energies of transition metal hydrides. Our results demonstrate that inclusion of triples amplitudes at the fragment level alone is insufficient; a perturbative treatment of the environment triples amplitudes is required. For many energy-difference applications, feedback from the environment triples amplitudes to the fragment amplitudes is not essential, but it does play a role in the very challenging CoH and FeH molecules. A very interesting finding from our study is that in some challenging cases, we need an improved (second-order) perturbative method for the SD amplitudes, going beyond the first-order one used in our earlier work. In conclusion, considering both cost and accuracy, the MP2CCSDT(pt) model is the most promising for future applications among the candidates considered here.

Shee, Avijit [University of California, Berkeley, ↗
DOE OSTI2022

State-selective probing of CO 2 autoionizing inner valence Rydberg states with attosecond extreme ultraviolet four-wave-mixing spectroscopy

Nonlinear spectroscopies can disentangle spectra that are congested due to inhomogeneous broadening. Here, in conjunction with theoretical calculations, attosecond extreme ultraviolet (XUV) four-wave-mixing (FWM) spectroscopy is utilized to probe the dynamics of autoionizing inner valence excited Rydberg states of the polyatomic molecule, CO 2 . This tabletop nonlinear technique employs a short attosecond XUV pulse train and two noncollinear, few-cycle near-infrared pulses to generate background-free XUV wave-mixing signals. FWM emission is observed from the n=5-7 states of the Henning sharp ndσ g Rydberg series that converges to the ionic $\widetilde{B}$ 2 Σ$^{+}_{u}$ state. However, these transient emission signals decay with lifetimes of 33 ± 6, 53 ± 2, and 94 ± 2 fs, respectively, which calculations show are consistent with the lifetimes of the short-lived n=6-8 members of the nsσ g character Henning diffuse Rydberg series. The oscillator strengths of transitions between states involved in all possible resonant FWM processes are calculated, verifying that the nonlinear spectra are dominated by pathways described by an initial excitation to the diffuse nsσ g Rydberg series and emission from the sharp ndσ g Rydberg series. The results substantiate not only that attosecond XUV FWM spectroscopy produces rigorous and meaningful measurements of ultrafast dynamics in polyatomic systems, but also that nonlinear spectroscopic techniques are versatile tools to selectively probe dynamics that are otherwise difficult to access.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Integrated photonic molecule Brillouin laser with a high-power sub-100-mHz fundamental linewidth

Photonic integrated lasers with an ultra-low fundamental linewidth and a high output power are important for precision atomic and quantum applications, high-capacity communications, and fiber sensing, yet wafer-scale solutions have remained elusive. Here we report an integrated stimulated Brillouin laser (SBL), based on a photonic molecule coupled resonator design, that achieves a sub-100-mHz fundamental linewidth with greater than 10-mW output power in the C band, fabricated on a 200-mm silicon nitride (Si 3 N 4 ) CMOS-foundry compatible wafer-scale platform. The photonic molecule design is used to suppress the second-order Stokes (S2) emission, allowing the primary lasing mode to increase with the pump power without phase noise feedback from higher Stokes orders. The nested waveguide resonators have a 184 million intrinsic and 92 million loaded Q, over an order of magnitude improvement over prior photonic molecules, enabling precision resonance splitting of 198 MHz at the S2 frequency. We demonstrate S2-suppressed single-mode SBL with a minimum fundamental linewidth of 71±18 mHz, corresponding to a 23±6-mHz 2 /Hz white-frequency-noise floor, over an order of magnitude lower than prior integrated SBLs, with an ∼11-mW output power and 2.3-mW threshold power. The frequency noise reaches the resonator-intrinsic thermo-refractive noise from 2-kHz to 1-MHz offset. The laser phase noise reaches −155 dBc/Hz at 10-MHz offset. The performance of this chip-scale SBL shows promise not only to improve the reliability and reduce size and cost but also to enable new precision experiments that require the high-speed manipulation, control, and interrogation of atoms and qubits. Realization in the silicon nitride ultra-low loss platform is adaptable to a wide range of wavelengths from the visible to infrared and enables integration with other components for systems-on-chip solutions for a wide range of precision scientific and engineering applications including quantum sensing, gravitometers, atom interferometers, precision metrology, optical atomic clocks, and ultra-low noise microwave generation.

Liu, Kaikai (ORCID:0000000213609646)↗
DOE OSTI2020

Materials Data on ClO2 by Materials Project

ClO2 crystallizes in the orthorhombic Pbca space group. The structure is zero-dimensional and consists of eight hypochlorous acid;hydrate molecules. there are two inequivalent O sites. In the first O site, O is bonded in a single-bond geometry to one Cl atom. The O–Cl bond length is 1.50 Å. In the second O site, O is bonded in a single-bond geometry to one Cl atom. The O–Cl bond length is 1.48 Å. Cl is bonded in a bent 120 degrees geometry to two O atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on H2O by Materials Project

H2O crystallizes in the trigonal R-3 space group. The structure is zero-dimensional and consists of thirty-six water molecules. there are two inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. In the second H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 1.00 Å. O2- is bonded in a water-like geometry to two H1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sb4IrC5ClO5F22 by Materials Project

IrCl(CO)5(Sb2F11)2 crystallizes in the monoclinic P2_1 space group. The structure is zero-dimensional and consists of ten formaldehyde molecules, two IrCl clusters, and four Sb2F11 clusters. In each IrCl cluster, Ir5+ is bonded in a single-bond geometry to one Cl1- atom. The Ir–Cl bond length is 2.37 Å. Cl1- is bonded in a distorted single-bond geometry to one Ir5+ atom. In each Sb2F11 cluster, there are two inequivalent Sb2+ sites. In the first Sb2+ site, Sb2+ is bonded to six F1- atoms to form corner-sharing SbF6 octahedra. The corner-sharing octahedral tilt angles are 28°. There are a spread of Sb–F bond distances ranging from 1.89–2.06 Å. In the second Sb2+ site, Sb2+ is bonded to six F1- atoms to form corner-sharing SbF6 octahedra. The corner-sharing octahedral tilt angles are 28°. There are a spread of Sb–F bond distances ranging from 1.89–2.09 Å. There are eleven inequivalent F1- sites. In the first F1- site, F1- is bonded in a single-bond geometry to one Sb2+ atom. In the second F1- site, F1- is bonded in a single-bond geometry to one Sb2+ atom. In the third F1- site, F1- is bonded in a single-bond geometry to one Sb2+ atom. In the fourth F1- site, F1- is bonded in a single-bond geometry to one Sb2+ atom. In the fifth F1- site, F1- is bonded in a single-bond geometry to one Sb2+ atom. In the sixth F1- site, F1- is bonded in a single-bond geometry to one Sb2+ atom. In the seventh F1- site, F1- is bonded in a single-bond geometry to one Sb2+ atom. In the eighth F1- site, F1- is bonded in a single-bond geometry to one Sb2+ atom. In the ninth F1- site, F1- is bonded in a bent 150 degrees geometry to two Sb2+ atoms. In the tenth F1- site, F1- is bonded in a single-bond geometry to one Sb2+ atom. In the eleventh F1- site, F1- is bonded in a single-bond geometry to one Sb2+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on H2O by Materials Project

H2O is alpha Pu-like structured and crystallizes in the triclinic P1 space group. The structure is zero-dimensional and consists of twelve water molecules. there are two inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. In the second H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 1.00 Å. O2- is bonded in a water-like geometry to two H1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on H2O by Materials Project

H2O is alpha Pu-like structured and crystallizes in the triclinic P1 space group. The structure is zero-dimensional and consists of twelve water molecules. there are two inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 1.00 Å. In the second H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 1.00 Å. O2- is bonded in a water-like geometry to two H1+ atoms. Both O–H bond lengths are 1.00 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on H2O by Materials Project

H2O is alpha Pu-like structured and crystallizes in the triclinic P1 space group. The structure is zero-dimensional and consists of twelve water molecules. there are two inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 1.00 Å. In the second H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 1.00 Å. O2- is bonded in a water-like geometry to two H1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on O2 by Materials Project

O2 is Cubic alpha N2 structured and crystallizes in the orthorhombic Pbca space group. The structure is zero-dimensional and consists of eight trioxidane molecules. there are two inequivalent O sites. In the first O site, O is bonded in a single-bond geometry to one O atom. The O–O bond length is 1.28 Å. In the second O site, O is bonded in a bent 120 degrees geometry to two equivalent O atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on H2SO4 by Materials Project

H2SO4 is Protactinium-like structured and crystallizes in the monoclinic Cc space group. The structure is zero-dimensional and consists of four sulfuric acid molecules. there are two inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. In the second H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. S6+ is bonded in a tetrahedral geometry to four O2- atoms. There are a spread of S–O bond distances ranging from 1.44–1.58 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one S6+ atom. In the second O2- site, O2- is bonded in a distorted water-like geometry to one H1+ and one S6+ atom. In the third O2- site, O2- is bonded in a bent 120 degrees geometry to one H1+ and one S6+ atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to one S6+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on H2SO4 by Materials Project

H2SO4 crystallizes in the monoclinic Cc space group. The structure is zero-dimensional and consists of four sulfuric acid molecules. there are two inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. In the second H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. S6+ is bonded in a tetrahedral geometry to four O2- atoms. There are a spread of S–O bond distances ranging from 1.43–1.59 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one S6+ atom. In the second O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one H1+ and one S6+ atom. In the third O2- site, O2- is bonded in a water-like geometry to one H1+ and one S6+ atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to one S6+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on H4SO5 by Materials Project

H4SO5 crystallizes in the monoclinic P2_1/c space group. The structure is zero-dimensional and consists of four sulfuric acid, monohydrate molecules. there are four inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. In the second H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. In the third H1+ site, H1+ is bonded in a linear geometry to two O2- atoms. There is one shorter (1.16 Å) and one longer (1.28 Å) H–O bond length. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. S6+ is bonded in a tetrahedral geometry to four O2- atoms. There are a spread of S–O bond distances ranging from 1.44–1.60 Å. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one S6+ atom. In the second O2- site, O2- is bonded in a trigonal non-coplanar geometry to three H1+ atoms. In the third O2- site, O2- is bonded in a single-bond geometry to one S6+ atom. In the fourth O2- site, O2- is bonded in a water-like geometry to one H1+ and one S6+ atom. In the fifth O2- site, O2- is bonded in a water-like geometry to one H1+ and one S6+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on S by Materials Project

S crystallizes in the trigonal P3 space group. The structure is zero-dimensional and consists of six trisulfane molecules. there are three inequivalent S sites. In the first S site, S is bonded in a single-bond geometry to one S atom. The S–S bond length is 1.94 Å. In the second S site, S is bonded in a bent 120 degrees geometry to two S atoms. The S–S bond length is 1.93 Å. In the third S site, S is bonded in a single-bond geometry to one S atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on H2O by Materials Project

H2O is Indium structured and crystallizes in the monoclinic Cc space group. The structure is zero-dimensional and consists of four water water molecules. there are four inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.97 Å. In the second H1+ site, H1+ is bonded in a distorted single-bond geometry to one O2- atom. The H–O bond length is 1.00 Å. In the third H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. In the fourth H1+ site, H1+ is bonded in a distorted linear geometry to two O2- atoms. There is one shorter (1.01 Å) and one longer (1.65 Å) H–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted water-like geometry to two H1+ atoms. In the second O2- site, O2- is bonded in a distorted water-like geometry to three H1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on H2O by Materials Project

H2O is Keatite structured and crystallizes in the tetragonal P4_12_12 space group. The structure is zero-dimensional and consists of twelve water molecules. there are two inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 1.00 Å. In the second H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. O2- is bonded in a water-like geometry to two H1+ atoms.

36 MATERIALS SCIENCE↗