Applied Physics and Materials Science

State-of-the-art many-body wave function techniques rely on heuristics to achieve high accuracy at an attainable cost to solve the many-body Schrödinger equation. By far the most common property used to assess accuracy has been the total energy; however, total energies do not give a complete picture of electron correlation.. In this work, the authors assess the von Neumann entropy of the one-particle reduced density matrix (1-RDM) to compare selected configuration interaction (CI), coupled cluster, variational Monte Carlo, and fixed-node diffusion Monte Carlo for benchmark hydrogen chains. A new algorithm, the circle reject method is presented which improves the efficiency of the evaluation of the von Neumann entropy using quantum Monte Carlo by several orders of magnitude. The von Neumann entropy of the 1-RDM and the eigenvalues of the 1-RDM are shown to distinguish between the dynamic correlation introduced by the Jastrow and static correlation introduced by determinants with large weights, confirming some of the lore in the field concerning the difference between the selected CI and Slater-Jastrow wave functions.

Gauge Theory plays a crucial role in many areas in science, including high energy physics, condensed matter physics and quantum information science. In quantum simulations of lattice gauge theory, an important step is to construct a wave function that obeys gauge symmetry. In this paper, we have developed gauge equivariant neural network wave function techniques for simulating continuous-variable quantum lattice gauge theories in the Hamiltonian formulation. We have applied the gauge equivariant neural network approach to find the ground state of 2 + 1-dimensional lattice gauge theory with U(1) gauge group using variational Monte Carlo. We have benchmarked our approach against the state-of-the-art complex Gaussian wave functions, demonstrating improved performance in the strong coupling regime and comparable results in the weak coupling regime.

We describe a new open-source Python-based package for high accuracy correlated electron calculations using quantum Monte Carlo (QMC) in real space: PyQMC. PyQMC implements modern versions of QMC algorithms in an accessible format, enabling algorithmic development and easy implementation of complex workflows. Tight integration with the PySCF environment allows for simple comparison between QMC calculations and other many-body wave function techniques, as well as access to high accuracy trial wave functions.

We describe a new open-source Python-based package for high accuracy correlated electron calculations using quantum Monte Carlo (QMC) in real space: PyQMC. PyQMC implements modern versions of QMC algorithms in an accessible format, enabling algorithmic development and easy implementation of complex workflows. Tight integration with the PySCF environment allows for a simple comparison between QMC calculations and other many-body wave function techniques, as well as access to high accuracy trial wave functions.

We report on a robust and sensitive approach for detecting protective antigen (PA) exotoxin from Bacillus anthracis in complex media. A peptide-based capture agent against PA was developed by improving a bacteria display-developed peptide into a highly selective biligand through in situ click screening against a large, chemically synthesized peptide library. This biligand was coupled with an electrochemical enzyme-linked immunosorbent assay utilizing nanostructured gold electrodes. The resultant assay yielded a limit of detection of PA of 170 pg/mL (2.1 pM) in buffer, with minimal sensitivity reduction in 1% serum. The powdered capture agent could be stably stored for several days at 65°C, and the full electrochemical biosensor showed no loss of performance after extended storage at 40°C. The engineered stability and specificity of this assay should be extendable to other cases in which biomolecular detection in demanding environments is required.

We report on a method to improve in vitro diagnostic assays that detect immune response, with specific application to HIV-1. The inherent polyclonal diversity of the humoral immune response was addressed by using sequential in situ click chemistry to develop a cocktail of peptide-based capture agents, the components of which were raised against different, representative anti-HIV antibodies that bind to a conserved epitope of the HIV-1 envelope protein gp41. The cocktail was used to detect anti-HIV-1 antibodies from a panel of sera collected from HIV-positive patients, with improved signal-to-noise ratio relative to the gold standard commercial recombinant protein antigen. The capture agents were stable when stored as a powder for two months at temperatures close to 60 o C.

Metrics & More Article Recommendations A n author's name was misspelled in the original byline: Sevan Chanakain should be listed as Sevan Chanakian. The corrected byline is given in this erratum. The conclusions of the work are not affected.

There are two crucial tasks for realizing high-efficiency polymer solar cells (PSCs): increasing the range of the spectral absorption of light and efficiently harvesting photogenerated excitons. Here, we describe Förster resonance energy transfer-based heterojunction polymer solar cells that incorporate squaraine dye. The high absorbance of squaraine in the near-infrared region broadens the spectral absorption of the solar cells and assists in developing an ordered nanomorphology for enhanced charge transport. Femtosecond spectroscopic studies reveal highly efficient (up to 96%) excitation energy transfer from poly(3-hexylthiophene) to squaraine occurring on a picosecond timescale. We demonstrate a 38% increase in power conversion efficiency to reach 4.5%, and suggest that this system has improved exciton migration over long distances. This architecture transcends traditional multiblend systems, allowing multiple donor materials with separate spectral responses to work synergistically, thereby enabling an improvement in light absorption and conversion. This opens up a new avenue for the development of high-efficiency polymer solar cells. P olymer solar cells (PSCs) are promising candidates for providing low-cost, lightweight, large-area and mechanically flexible energy conversion devices 1-4 . Cells incorporating a binary bulk heterojunction (BHJ) blend based on regioregular poly(3hexylthiophene) (P3HT) and [6,6]-phenyl-C 61 -butyric acid methyl ester (PCBM) have been studied widely, providing power conversion efficiencies (PCEs) of 4-5% (refs 5-8). A critical step towards improving the PCE is to increase the quantum yields of incident photons. P3HT, with its bandgap of 2 eV, is only able to harvest 22% of the total photons in solar light 9,10 . A common route towards realizing broadband light harvesting makes use of lowbandgap polymers, which often require processing additives 11-14 , making it difficult to precisely control both the crystallinity and phase separation of the photoactive layer. Additionally, the photogenerated excitons in the photoactive layer must reach the donor-acceptor interface to dissociate before recombination 4 . Unfortunately, an ideally bicontinuous interpenetration network is difficult to control 15 , and results in 50% energy loss to recombination 16 . Recent studies in dye-sensitized solar cells have demonstrated that Förster resonance energy transfer (FRET) is a promising strategy to improve exciton migration over long distances . Although it was thought that FRET may occur in P3HT-TiO 2 nanostructured solar cells featuring squaraine dye 22 , to the best of our knowledge, experimental evidence that FRET can enhance exciton harvesting in polymer BHJ solar cells has never been presented. Furthermore, several groups have studied ternary-blend PSCs that utilize a third material 23 to either extend the solar spectrum or control the phase separation 30 . In many cases, however, the third material in PSCs, such as porphyrin-based dye, has even reduced device performance through the formation of recombination centres and/or detrimental effects on blend morphology 24,25 .

For a crystal to exhibit nonlinear optical (NLO) activity such as second-harmonic generation (SHG), it must belong to a noncentrosymmetric (NCS) space group. Moreover, for these nonlinear optical (NLO) materials to be suitable for practical uses, the synthesized crystals should be phase-matchable (PM). Previous synthetic research into SHGactive crystals has centered on (i) how to create NCS compounds and/or (ii) how to obtain NCS compounds with high SHG efficiencies. With these tactics, one can synthesize a material with a high SHG efficiency, but the material could be unusable if the material was nonphase-matchable (non-PM). To probe the origin of phase matchability of NCS structures, we present two new chemically similar hybrid compounds within one composition space: (I) [Hdpa] 2 NbOF 5 ·2H 2 O and (II) HdpaNbOF 4 (dpa = 2,2′-dipyridylamine). Both compounds are NCS and chemically similar, but (I) is non-PM while (II) is PM. Our results indicateconsistent with organic crystallographythe arrangement of the organic molecule within hybrid materials dictates whether the material is PM or non-PM.

Small organic molecules, like ethane and benzene, are ubiquitous in the atmosphere and surface of Saturn’s largest moon Titan, forming plains, dunes, canyons, and other surface features. Understanding Titan’s dynamic geology and designing future landing missions requires sufficient knowledge of the mechanical characteristics of these solid-state organic minerals, which is currently lacking. To understand the deformation and mechanical properties of a representative solid organic material at space-relevant temperatures, we freeze liquid micro-droplets of benzene to form ~10 μm-tall single-crystalline pyramids and uniaxially compress them in situ. These micromechanical experiments reveal contact pressures decaying from ~2 to ~0.5 GPa after ~1 μm-reduction in pyramid height. The deformation occurs via a series of stochastic (~5-30 nm) displacement bursts, corresponding to densification and stiffening of the compressed material during cyclic loading to progressively higher loads. Molecu...

Natural hard composites like human bone possess a combination of strength and toughness that exceeds that of their constituents and of many engineered composites. This augmentation is attributed to their complex hierarchical structure, spanning multiple length scales; in bone, characteristic dimensions range from nanoscale fibrils to microscale lamellae to mesoscale osteons and macroscale organs. The mechanical properties of bone have been studied, with the understanding that the isolated microstructure at micro- and nano-scales gives rise to superior strength compared to that of whole tissue, and the tissue possesses an amplified toughness relative to that of its nanoscale constituents. Nanoscale toughening mechanisms of bone are not adequately understood at sample dimensions that allow for isolating salient microstructural features, because of the challenge of performing fracture experiments on small-sized samples. We developed an in situ three-point bend experimental methodology ...