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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 631 records · Page 35
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Second Linear Response Theory and the Analytic Calculation of Excited-State Properties

We present a method based on second linear response time-dependent density func- tional theory (TDDFT) to calculate permanent and transition multipoles of excited states, which are required to compute excited-state absorption/emission spectra, multi- photon optical processes, among others. In previous work, we examined computations based on second linear response theory in which linear response TDDFT was employed twice. In contrast, the present methodology only requires information from a single linear response calculation to compute the excited-state properties. These are eval- uated analytically through various algebraic operations involving electron repulsion integrals and excitation vectors. The present derivation focuses on full many-body wave functions instead of single orbitals, as in our previous approach. Here, we test the proposed method by applying it to several diatomic and triatomic molecules. This shows that the computed excited-state dipoles are consistent with respect to reference equation-of-motion coupled cluster calculations.

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

Development of $\mathrm{AMOEBA}$ Polarizable Force Field for Rare-Earth La 3+ Interaction with Bioinspired Ligands

Rare-earth metals (REMs) are crucial for many important industries, such as power generation and storage, in addition to cancer treatment and medical imaging. One promising new REM refinement approach involves mimicking the highly selective and efficient binding of REMs observed in relatively recently discovered proteins. However, realizing any such bioinspired approach requires an understanding of the biological recognition mechanisms. In this report we developed a new classical polarizable force field based on the AMOEBA framework for modeling a lanthanum ion (La 3+ ) interacting with water, acetate, and acetamide, which have been found to coordinate the ion in proteins. The parameters were derived by comparing to high-level ab initio quantum mechanical (QM) calculations that include relativistic effects. The AMOEBA model, with advanced atomic multipoles and electronic polarization, is successful in capturing both the QM distance-dependent La 3+ –ligand interaction energies and experimental hydration free energy. A new scheme for pairwise polarization damping (POLPAIR) was developed to describe the polarization energy in La 3+ interactions with both charged and neutral ligands. Simulations of La3+ in water showed water coordination numbers and ion–water distances consistent with previous experimental and theoretical findings. Water residence time analysis revealed both fast and slow kinetics in water exchange around the ion. This new model will allow investigation of fully solvated lanthanum ion–protein systems using GPU-accelerated dynamics simulations to gain insights on binding selectivity, which may be applied to the design of synthetic analogues.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Understanding Chemical Bonding in Alloys and the Representation in Atomistic Simulations

Alloys are widely used in catalysts and structural materials. The nature of chemical bonding and the origin of alloy formation energies, defect energies, and interfacial properties have not been well understood to date but are critical to material performance. In this contribution, we explain the polar nature of chemical bonding and an implementation in classical and reactive atomistic simulations to understand such properties more quantitatively. Electronegativity differences between metal atoms lead to polar bonding, and exothermic alloy formation energies are related to charge transfer between the different elements. These differences can be quantified by atomic charges using pairwise charge increments, determined by matching the computed alloy formation energy to experimentally measured alloy formation energies using pair potentials for the pure metals. The polar character of alloys is comparable to organic molecules and partially ionic minerals, for example, AlNi and AlNi3 alloys assume significant atomic charges of ±0.40e and +0.60e/–0.20e, respectively. The subsequent analysis of defect sites and defect energies using force-field-based calculations shows excellent agreement with calculations using density functional theory and embedded atom models (EAM). The formation of vacancy and antisite defects is characterized by a redistribution of charge in the first shell of neighbor atoms in the classical models whereby electroneutrality is maintained and charge increments correlate with differences in electronegativity. The proposed atomic charges represent internal dipole and multipole moments, consistent with existing definitions for organic and inorganic compounds and with the extended Born model (Heinz, H.; Suter, U. W. J. Phys. Chem. B2004,108 (47), 18341–18352). The method can be applied to any alloy and has a reproducibility of ±10%. In contrast, quantum mechanical charge schemes remain associated with deviations exceeding ±100%. The atomic charges for alloys provide a simple initial measure for the internal electronic structure, surface adsorption of molecules, and reactivity in catalysis and corrosion. The models are compatible with the Interface force field (IFF), CHARMM, AMBER, OPLS-AA, PCFF, CVFF, and GROMOS for reliable atomistic simulations of alloys and their interfaces with minerals and electrolytes from the nanometer scale to the micrometer scale.

Chemistry↗
DOE OSTI2025

Completely Multipolar Model for Many-Body Water–Ion and Ion–Ion Interactions

This work constructs an advanced force field, the Completely Multipolar Model (CMM), to quantitatively reproduce each term of an energy decomposition analysis (EDA) for aqueous solvated alkali metal cations and halide anions and their ion pairings. We find that all individual EDA terms remain well-approximated in the CMM for ion-water and ion-ion interactions, except for polarization, which shows errors due to the partial covalency of ion interactions near their equilibrium. We quantify the onset of the dative bonding regime by examining the change in molecular polarizability and Mayer bond indices as a function of distance, showing that partial covalency manifests by breaking the symmetry of atomic polarizabilities while strongly damping them at short-range. This motivates an environment-dependent atomic polarizability parameter that depends on the strength of the local electric field experienced by the ions to account for strong damping, with anisotropy introduced by atomic multipoles. The resulting CMM model for ions provides accurate dimer surfaces and three-body polarization and charge transfer compared to EDA, and shows excellent performance on various ion benchmarks including vibrational frequencies and cluster geometries.

Heindel, Joseph P↗
DOE OSTI2022

Design and Preparation of Nematic Colloidal Particles

Colloidal systems are abundant in technology, in biomedical settings, and in our daily life. The so-called “colloidal atoms” paradigm exploits interparticle interactions to self-assemble colloidal analogs of atomic and molecular crystals, liquid crystal glasses, and other types of condensed matter from nanometer- or micrometer-sized colloidal building blocks. Nematic colloids, which comprise colloidal particles dispersed within an anisotropic nematic fluid host medium, provide a particularly rich variety of physical behaviors at the mesoscale, not only matching but even exceeding the diversity of structural and phase behavior in conventional atomic and molecular systems. This feature article, using primarily examples of works from our own group, highlights recent developments in the design, fabrication, and self-assembly of nematic colloidal particles, including the capabilities of preprogramming their behavior by controlling the particle’s surface boundary conditions for liquid crystal molecules at the colloidal surfaces as well as by defining the shape and topology of the colloidal particles. Here recent progress in defining particle-induced defects, elastic multipoles, self-assembly, and dynamics is discussed along with open issues and challenges within this research field.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Photoluminescence Enhancement through Symmetry Breaking Induced by Defects in Nanocrystals

We present a theoretical model for the effect of symmetry breaking introduced by the doping of semiconductor nanocrystals with Coulomb impurities. The presence of a Coulomb center breaks the nanocrystal symmetry and affects its optical properties through the mixing of the hole spin and parity sublevels, breaking the selection rules responsible for the exciton dark state in undoped nanocrystals. After reviewing the effects on the exciton fine structure and optical selection rules using symmetry theory, we present a perturbative model to quantify the effects. We find that the symmetry breaking proceeds by two mechanisms: First, mixing by even parity terms in the Coulomb multipole expansion results in an exciton fine structure consisting of three optically active doublets which are polarized along x, y, and z axes with a ground optically passive dark exciton state, and second, odd parity terms which break inversion symmetry significantly activate optical transitions which are optically forbidden in the unperturbed nanocrystal due to both spin and parity selection rules. In the case of small sized “quasi-spherical” nanocrystals, the introduction of a single positively charged Coulomb center is shown here to result in significant enhancement of the radiative decay rate at room temperatures by up to a factor of 10.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2020

Active Plasmonics and Active Chiral Plasmonics through Orientation-Dependent Multipolar Interactions

While most active plasmonic efforts focus on responsive metamaterials to modulate optical response, we present a simple alternative based on applied orientation control that can likely be implemented for many passive plasmonic materials. Passive plasmonic motifs are simpler to prepare but cannot be altered postfabrication. Here, we show that such systems can be easily manipulated through substrate orientation control to generate both active plasmonic and active chiral plasmonic responses. Using gold nanocrescents as our model platform, we demonstrate tuning of optical extinction from -21% to +36% at oblique incidence relative to normal incidence. Variation of substrate orientation in relation to incident polarization is also demonstrated to controllably switch chiroptical handedness (e.g., Δg = ± 0.55). These active plasmonic responses arise from the multipolar character of resonant modes. In particular, we correlate magnetoelectric and dipole–quadrupole polarizabilities with different light-matter orientation-dependence in both near- and far-field localized surface plasmon activity. Additionally, the attribution of far-field optical response to higher-order multipoles highlights the sensitivity offered by these orientation-dependent characterization techniques to probe the influence of localized electromagnetic field gradients on a plasmonic response. The sensitivity afforded by orientation-dependent optical characterization is further observed by the manifestation in both plasmon and chiral plasmon responses of unpredicted structural nanocrescent variance (e.g., left- and right-tip asymmetry) not physically resolved through topographical imaging.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2011

The Roles of Molecular Structure and Effective Optical Symmetry in Evolving Dipolar Chromophoric Building Blocks to Potent Octopolar Nonlinear Optical Chromophores

A series of mono-, bis-, tris-, and tetrakis(porphinato)zinc(II) (PZn)-elaborated ruthenium(II) bis(terpyridine) (Ru) complexes have been synthesized in which an ethyne unit connects the macrocycle meso carbon atom to terpyridyl (tpy) 4-, 4²-, and 4²-positions. These supermolecular chromophores, based on the ruthenium(II) [5-(4²-ethynyl-(2,2²;6²,2²-terpyridinyl))-10,20-bis(2²,6²-bis(3,3-dimethyl-1-butyloxy)phenyl)porphinato]zinc(II)-(2,2²;6²,2²-terpyridine)2+ bis-hexafluorophosphate (RuPZn) archetype, evince strong mixing of the PZn-based oscillator strength with ruthenium terpyridyl charge resonance bands. Potentiometric and linear absorption spectroscopic data indicate that for structures in which multiple PZn moieties are linked via ethynes to a [Ru(tpy)2]2+ core, little electronic coupling is manifest between PZn units, regardless of whether they are located on the same or opposite tpy ligand. Congruent with these experiments, pump probe transient absorption studies suggest that the individual RuPZn fragments of these structures exhibit, at best, only modest excited-state electronic interactions that derive from factors other than the dipole dipole interactions of these strong oscillators; this approximate independent character of the component RuPZn oscillators enables fabrication of nonlinear optical (NLO) multipoles with extraordinary hyperpolarizabilities. Dynamic hyperpolarizability (βλ) values and depolarization ratios (Ï) were determined from hyper-Rayleigh light scattering (HRS) measurements carried out at an incident irradiation wavelength (λinc) of 1300 nm. The depolarization ratio data provide an experimental measure of chromophore optical symmetry; appropriate coupling of multiple charge-transfer oscillators produces structures having enormous averaged hyperpolarizabilities (βHRS values), while evolving the effective chromophore symmetry from purely dipolar (e.g., Ru(tpy)[4-(Zn-porphyrin)ethynyl-tpy](PF6)2, βHRS = 1280 10-30 esu, Ï = 3.8; Ru(tpy)[4²-(Zn-porphyrin)ethynyl-tpy](PF6)2, βHRS = 2100 10-30 esu, Ï = 3.8) to octopolar (e.g., Ru[4,4²-bis(Zn-porphyrin)ethynyl-tpy]2(PF6)2, βHRS = 1040 10-30 esu, Ï = 1.46) via structural motifs that possess intermediate values of the depolarization ratio. The chromophore design roadmap provided herein gives rise to octopolar supermolecules that feature by far the largest off-diagonal octopolar first hyperpolarizability tensor components ever reported, with the effectively octopolar Ru[4,4²-bis(Zn-porphyrin)ethynyl-tpy]2(PF6)2 possessing a βHRS value at 1300 nm more than a factor of 3 larger than that determined for any chromophore having octopolar symmetry examined to date. Because NLO octopoles possess omnidirectional NLO responses while circumventing the electrostatic interactions that drive bulk-phase centrosymmetry for NLO dipoles at high chromophore concentrations, the advent of octopolar NLO chromophores having vastly superior βHRS values at technologically important wavelengths will motivate new experimental approaches to achieve acentric order in both bulk-phase and thin film structures.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Intermolecular Interactions in Direct Air Capture Materials: Insights from Charge Density Analysis

Direct air capture (DAC) materials enable the removal of CO 2 from the atmosphere, but improving their efficiency requires a detailed understanding of the intermolecular interactions that govern CO 2 sorption and release. Here, we present an experimental electron density study of methylglyoxal-bis(iminoguanidine) (MGBIG), a promising DAC material, using high-resolution X-ray and neutron diffraction data combined with quantum crystallographic analysis. This approach bridges theoretical and experimental data by quantifying electron density distributions and revealing how hydrogen bonds stabilize CO 2 -derived carbonate phases and may influence the desorption behavior. We identify distinct hydrogen-bonding environments in two crystalline carbonate phases: P1, a transient kinetic product, and P3, a thermodynamically stable phase. Multipolar refinement and electrostatic potential and multipole moment calculations precisely map electron density distributions, revealing key hydrogen bonds involved in CO 2 capture. Topological analysis of electron density highlights a cooperative hydrogen-bonding network in the thermodynamically favored P3 phase, where enhanced electron density delocalization and water-mediated interactions contribute to a more stable lattice. Energetic analyses confirm that stronger hydrogen bonding networks enhance the stability of P3 with a binding energy of −607.0 kJ/mol and greater lattice stability (−847.3 kJ/mol) compared to P1 (−302.5 and −571.0 kJ/mol, respectively). Electrostatic potential maps further illustrate polarization patterns that may influence the stability of the binding of CO 2 and release conditions. These findings establish a direct experimental framework for linking electron density distributions to intermolecular interactions in DAC materials, providing a rational design strategy for optimizing sorbents with improved CO 2 capture efficiency and reduced energy demands.

Electron density↗
DOE OSTI2025

Symmetrization of Strong Hydrogen Bond under High Pressure in Bihydroxide-Ion-Containing NaCu 2 (SO 4 ) 2 ·H 3 O 2 Revealed by Experimental Charge Density, Single-Crystal Electron Diffraction, and Neutron Diffraction Studies

In minerals and inorganic compounds, strong hydrogen bonding can lead to the formation of complex ionic species such as the H 3 O 2 – bihydroxide anion and Zundel cation H 5 O 2 + . We studied [NaCu 2 (SO 4 ) 2 ·H 3 O 2 ] natrochalcite, which contains bihydroxide anions and undergoes hydrogen bond symmetrization at the lowest pressure reported so far among inorganic compounds. Hydrogen bond symmetrization leads to changes in the bulk modulus, seismic wave velocities, and proton mobility and plays a primary role in high-temperature superconductivity, but its characteristics are not well understood due to a lack of systematic studies and limitations of experimental methods sensitive to this subtle change. In this work, we applied experimental charge density analysis based on in situ single-crystal X-ray diffraction data, along with the single-crystal neutron and electron diffraction experiments, to probe the behavior of hydrogen atoms during the hydrogen bond symmetrization process under high-pressure conditions. On the way to the symmetrical H-bonding, natrochalcite undergoes a series of complex redistributions of electron density, which we trace with multipole refinement and detailed analysis of changes in the Laplacian of electron density values. Additionally, we deconvoluted the equation of state (volume of the unit cell vs pressure relation) into the atomic equation of states describing dependencies of atomic charges or volumes vs pressure.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Volume Flow Rate Estimation for Small Explosions at Mt. Etna, Italy, From Acoustic Waveform Inversion

Rapid assessment of the volume and the rate at which gas and pyroclasts are injected into the atmosphere during volcanic explosions is key to effective eruption hazard mitigation. Here, we use data from a dense infrasound network deployed in 2017 on Mt. Etna, Italy, to estimate eruptive volume flow rates (VFRs) during small gas-and-ash explosions. We use a finite-difference time-domain approximation to compute the acoustic Green's functions and perform a full waveform inversion for a multipole source, combining monopole and horizontal dipole terms. The inversion produces realistic estimates of VFR, on the order of 4 × 10 4 m 3 /s and well-defined patterns of source directivity. This is the first application of acoustic waveform inversion at Mt. Etna. Our results demonstrate that acoustic waveform inversion is a mature and robust tool for assessment of source parameters and holds potential as a tool to provide rapid estimates of VFR in near real time.

58 GEOSCIENCES↗
DOE OSTI2021

X-ray study of ferroic octupole order producing anomalous Hall effect

Recently found anomalous Hall, Nernst, magnetooptical Kerr, and spin Hall effects in the antiferromagnets Mn 3 X (X = Sn, Ge) are attracting much attention for spintronics and energy harvesting. Since these materials are antiferromagnets, the origin of these functionalities is expected to be different from that of conventional ferromagnets. Here, we report the observation of ferroic order of magnetic octupole in Mn 3 Sn by X-ray magnetic circular dichroism, which is only predicted theoretically so far. The observed signals are clearly decoupled with the behaviors of uniform magnetization, indicating that the present X-ray magnetic circular dichroism is not arising from the conventional magnetization. We have found that the appearance of this anomalous signal coincides with the time reversal symmetry broken cluster magnetic octupole order. Our study demonstrates that the exotic material functionalities are closely related to the multipole order, which can produce unconventional cross correlation functionalities.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Quantum mechanical static dipole polarizabilities in the QM7b and AlphaML showcase databases

While density functional theory (DFT) is often an accurate and efficient methodology for evaluating molecular properties such as energies and multipole moments, this approach often yields larger errors for response properties such as the dipole polarizability (α), which describes the tendency of a molecule to form an induced dipole moment in the presence of an electric field. In this work, we provide static α tensors (and other molecular properties such as total energy components, dipole and quadrupole moments, etc.) computed using quantum chemical (QC) and DFT methodologies for all 7,211 molecules in the QM7b database. We also provide the same quantities for the 52 molecules in the AlphaML showcase database, which includes the DNA/RNA nucleobases, uncharged amino acids, several open-chain and cyclic carbohydrates, five popular pharmaceutical molecules, and 23 isomers of C 8 H n . All QC calculations were performed using linear-response coupled-cluster theory including single and double excitations (LR-CCSD), a sophisticated approach for electron correlation, and the d-aug-cc-pVDZ basis set to mitigate basis set incompleteness error. DFT calculations employed the B3LYP and SCAN0 hybrid functionals, in conjunction with d-aug-cc-pVDZ (B3LYP and SCAN0) and d-aug-cc-pVTZ (B3LYP).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

The ANI-1ccx and ANI-1x data sets, coupled-cluster and density functional theory properties for molecules

Abstract Maximum diversification of data is a central theme in building generalized and accurate machine learning (ML) models. In chemistry, ML has been used to develop models for predicting molecular properties, for example quantum mechanics (QM) calculated potential energy surfaces and atomic charge models. The ANI-1x and ANI-1ccx ML-based general-purpose potentials for organic molecules were developed through active learning; an automated data diversification process. Here, we describe the ANI-1x and ANI-1ccx data sets. To demonstrate data diversity, we visualize it with a dimensionality reduction scheme, and contrast against existing data sets. The ANI-1x data set contains multiple QM properties from 5 M density functional theory calculations, while the ANI-1ccx data set contains 500 k data points obtained with an accurate CCSD(T)/CBS extrapolation. Approximately 14 million CPU core-hours were expended to generate this data. Multiple QM calculated properties for the chemical elements C, H, N, and O are provided: energies, atomic forces, multipole moments, atomic charges, etc. We provide this data to the community to aid research and development of ML models for chemistry.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Quantum mechanical dataset of 836k neutral closed-shell molecules with up to 5 heavy atoms from C, N, O, F, Si, P, S, Cl, Br

Abstract We introduce the Vector-QM24 (VQM24) dataset comprehensively covering all possible neutral closed-shell small organic and inorganic molecules with up to five heavy (p-block) atoms: C, N, O, F, Si, P, S, Cl, Br. All valid stoichiometries, Lewis-rule-consistent graphs, and stable conformers (identified via GFN2-xTB) were enumerated combinatorially, yielding 577k conformational isomers spanning 258k constitutional isomers and 5,599 unique stoichiometries. DFT (ωB97X-D3/cc-pVDZ) optimizations were performed for all, and diffusion quantum Monte Carlo (DMC@PBE0(ccECP/cc-pVQZ)) energies are provided for 10,793 lowest-energy conformers with up to 4 heavy atoms. VQM24 includes structures, vibrational modes, rotational constants, thermodynamic properties (Gibbs free energies, enthalpies, ZPVEs, entropies, heat capacities), and electronic properties such as atomization, electron interaction, exchange-correlation, dispersion energies, multipole moments (dipole to hexadecapole), alchemical potentials, Mulliken charges, and wavefunctions. Machine learning models of atomization energies on this dataset reveal significantly higher complexity than QM9, with none achieving chemical accuracy. VQM24 offers a rigorous, high-fidelity benchmark for evaluating quantum machine learning models.

Science & Technology - Other Topics↗
DOE OSTI2014

Planck 2013 results. VII. HFI time response and beams

This paper characterizes the effective beams, the effective beam window functions and the associated errors for the Planck High Frequency Instrument (HFI) detectors. The effective beam is the angular response including the effect of the optics, detectors, data processing and the scan strategy. The window function is the representation of this beam in the harmonic domain which is required to recover an unbiased measurement of the cosmic microwave background angular power spectrum. The HFI is a scanning instrument and its effective beams are the convolution of: a) the optical response of the telescope and feeds; b) the processing of the time-ordered data and deconvolution of the bolometric and electronic transfer function; and c) the merging of several surveys to produce maps. The time response transfer functions are measured using observations of Jupiter and Saturn and by minimizing survey difference residuals. The scanning beam is the post-deconvolution angular response of the instrument, and is characterized with observations of Mars. The main beam solid angles are determined to better than 0.5% at each HFI frequency band. Observations of Jupiter and Saturn limit near sidelobes (within 5°) to about 0.1% of the total solid angle. Time response residuals remain as long tails in the scanning beams, but contribute less than 0.1% of the total solid angle. The bias and uncertainty in the beam products are estimated using ensembles of simulated planet observations that include the impact of instrumental noise and known systematic effects. Here, the correlation structure of these ensembles is well-described by five error eigenmodes that are sub-dominant to sample variance and instrumental noise in the harmonic domain. A suite of consistency tests provide confidence that the error model represents a sufficient description of the data. The total error in the effective beam window functions is below 1% at 100 GHz up to multipole ℓ ~ 1500, and below 0.5% at 143 and 217 GHz up to ℓ ~ 2000.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Planck 2013 results. III. LFI systematic uncertainties

We present the current estimate of instrumental and systematic effect uncertainties for the Planck -Low Frequency Instrument relevant to the first release of the Planck cosmological results. Here, we give an overview of the main effects and of the tools and methods applied to assess residuals in maps and power spectra. We also present an overall budget of known systematic effect uncertainties, which are dominated by sidelobe straylight pick-up and imperfect calibration. However, even these two effects are at least two orders of magnitude weaker than the cosmic microwave background fluctuations as measured in terms of the angular temperature power spectrum. A residual signal above the noise level is present in the multipole range &ell; < 20, most notably at 30 GHz, and is probably caused by residual Galactic straylight contamination. Current analysis aims to further reduce the level of spurious signals in the data and to improve the systematic effects modelling, in particular with respect to straylight and calibration uncertainties.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Planck 2013 results. XXV. Searches for cosmic strings and other topological defects

Planck data have been used to provide stringent new constraints on cosmic strings and other defects. We describe forecasts of the CMB power spectrum induced by cosmic strings, calculating these from network models and simulations using line-of-sight Boltzmann solvers. We have studied Nambu-Goto cosmic strings, as well as field theory strings for which radiative effects are important, thus spanning the range of theoretical uncertainty in the underlying strings models. We have added the angular power spectrum from strings to that for a simple adiabatic model, with the extra fraction defined as f 10 at multipole = 10. This parameter has been added to the standard six parameter fit using COSMOMC with flat priors. For the Nambu-Goto string model, we have obtained a constraint on the string tension of G μ/c 2 < 1.5 × 10 -7 and f 10 < 0.015 at 95% confidence that can be improved to G μ/c 2 < 1.3 × 10-7 and f 10 < 0.010 on inclusion of high-&ell; CMB data. For the Abelian-Higgs field theory model we find, G μ AH /c 2 < 3.2 × 10 -7 and f 10 < 0.028. The marginalised likelihoods for f 10 and in the f 10 -Ω b h 2 plane are also presented. We have additionally obtained comparable constraints on f 10 for models with semilocal strings and global textures. In terms of the effective defect energy scale these are somewhat weaker at G μ/c 2 < 1.1 × 10 -6 . We have made complementarity searches for the specific non-Gaussian signatures of cosmic strings, calibrating with all-sky Planck resolution CMB maps generated from networks of post-recombination strings. We have validated our non-Gaussian searches using these simulated maps in a Planck -realistic context, estimating sensitivities of up to Δ G μ/c 2 &approx; 4 × 10 -7 . We have obtained upper limits on the string tension at 95% confidence of G μ/c 2 < 9.0 × 10 -7 with modal bispectrum estimation and G μ/c 2 < 7.8 × 10 -7 for real space searches with Minkowski functionals. These are conservative upper bounds because only post-recombination string contributions have been included in the non-Gaussian analysis.

79 ASTRONOMY AND ASTROPHYSICS↗