L. L. Daemen

Los Alamos National Laboratory, Лос-Аламос, California, United States

Are you L. L. Daemen?

Claim your profile

Publications (220)435.73 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The atomic structures of calcium silicate hydrate (C–S–H) and calcium (–sodium) aluminosilicate hydrate (C–(N)–A–S–H) gels, and their presence in conventional and blended cement systems, have been the topic of significant debate over recent decades. Previous investigations have revealed that synthetic C–S–H gel is nanocrystalline and due to the chemical similarities between ordinary Portland cement (OPC)-based systems and low-CO2 alkali-activated slags, researchers have inferred that the atomic ordering in alkali-activated slag is the same as in OPC–slag cements. Here, X-ray total scattering is used to determine the local bonding environment and nanostructure of C(–A)–S–H gels present in hydrated tricalcium silicate (C3S), blended C3S–slag and alkali-activated slag, revealing the large intrinsic differences in the extent of nanoscale ordering between C–S–H derived from C3S and alkali-activated slag systems, which may have a significant influence on thermodynamic stability, and material properties at higher length scales, including long term durability of alkali-activated cements.
    Cement and Concrete Research 01/2015; 67:66–73. DOI:10.1016/j.cemconres.2014.08.006 · 3.85 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In this work, we investigated the systems of (Li, Ca)-O-(Cl, Br) under high pressure and temperature for the synthesis of lithium-rich anti-perovskite (LiRAP) halides. We successfully synthesized Li3-xCax/2OCl anti-perovsldte with x = 0.0, 0.1, 02 near 0.5 GPa and temperatures of 400-425 K and Li3OBr anti-perovskite at 3.0 GPa and 450 K. Different from the synthetic route previously reported at ambient pressure, LiA + 2LiOH --> Li(3)OA + H2O, the LiRAP halides under high P-T conditions are formed by dehydration of end-member and Ca-doped halide hydrates with a general formula of Li(2x + 1)A(OH)(2y), where A can be Cl or Br and x must be equal to y. This proposed formula predicts several new halide hydrates including Li3Cl(OH)(2), Li5Cl(OH)(4), Li3Br(OH)(2), and Li5Br(OH)(4), indicating that halide hydrates are structurally flexible to accommodate a range of lithium and hydroxide occupancies in the puckered layers of [Li2x + (1)(OH)(2y)(+)].
    Inorganic Chemistry Communications 10/2014; 48:140–143. DOI:10.1016/j.inoche.2014.08.036 · 2.06 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Anti-perovskite solid electrolyte films were prepared by pulsed laser deposition, and their room-temperature ionic conductivity can be improved by more than an order of magnitude in comparison with its bulk counterpart. The cyclability of Li3OCl films in contact with lithium was evaluated using a Li/Li3OCl/Li symmetric cell, showing self-stabilization during cycling test.
    Chemical Communications 08/2014; 50(78). DOI:10.1039/c4cc05372a · 6.72 Impact Factor
  • ECS Transactions 05/2014; 61(1):159-168. DOI:10.1149/06101.0159ecst
  • [Show abstract] [Hide abstract]
    ABSTRACT: Amorphous calcium/magnesium carbonates are of significant interest in the technology sector for a range of processes, including carbon storage and biomineralization. Here, the atomic structure of one hydrated amorphous magnesium carbonate (hydrated AMC, MgCO3·3D2O) is investigated using an iterative methodology, where quantum chemistry and experimental total scattering data are combined in an interactive iterative manner to produce an experimentally valid structural representation that is thermodynamically stable. The atomic structure of this hydrated AMC consists of a distribution of Mg2+ coordination states, predominately V- and VI-fold, and is heterogeneous due to the presence of Mg2+/CO32--rich regions interspersed with small ‘pores’ of water molecules. This heterogeneity at the atomic length scale is likely to contribute to the dehydration of hydrated AMC by providing a route for water molecules to be removed. We show that this iterative methodology enables wide sampling of the potential energy landscape, which is important for elucidating the true atomic structure of highly disordered metastable materials.
    Chemistry of Materials 04/2014; 26(8):2693–2702. DOI:10.1021/cm500470g · 8.54 Impact Factor
  • 2014 APS March Meeting, Denver CO; 03/2014
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: New challenges in neutron scattering result in an increased demand in novel moderator concepts. The most direct way to address the problem would be to change the moderator material itself. However the range of available neutron moderator materials is small. In this paper, we discuss triphenylmethane, a possible moderator material especially promising for cold neutron moderator applications. Our investigations include a parallel experimental and theoretical approach ranging from cross-section measurements and inelastic neutron spectroscopy to molecular modeling.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 02/2014; 738:1. DOI:10.1016/j.nima.2013.11.063 · 1.32 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: This study focuses on the interplay of molecular flexibility and hydrogen bonding manifested in the monoclinic (form I) and orthorhombic (form II) polymorphs of paracetamol. By means of incoherent inelastic neutron scattering and density functional theory calculations, the relaxation processes related to the methyl side group reorientation were analysed in detail. Our computational study demonstrates the importance of considering quantum effects to explain how methyl reorientations and subtle conformational changes of the molecule are intertwined. Indeed, by analysing the QENS of the neutron data, we were able to show a unique and complex motional flexibility in form II, reflected by a coupling between the methyl and the phenyl reorientation. This is associated with a higher energy barrier of the methyl rotation and a lower Gibbs free energy, when compared to form I. In conclusion, we put forward the idea that correlating solubility and molecular flexibility, through the relation between pKa and methyl rotation activation energy, might bring new insights to understanding and predicting drug bioavailability.
    Molecular Pharmaceutics 02/2014; 11(3). DOI:10.1021/mp400707m · 4.79 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The aim of this work was to describe the vibrations connected with the short hydrogen bonds of differing geometries in 2,4-dinitrobenzoic acid and in 2,4-dinitrobenzoic acid complexed in two ratios with pyridine. All three compounds contain short hydrogen bonds either between two acid molecules (OH⋯⋯O bond) or between acid and pyridine (NH⋯⋯O bonds) or both. We selectively deuterated the proton of the 2,4-dinitrobenzoic acid molecule involved in the proton transfer to aid in the assignment of the H-bond protonic modes. The compounds have been characterized with single crystal X-ray diffraction, CHN elemental analysis, FT-IR and IINS spectroscopy. We show that our combination of analytical methods with DFT calculations represents a fruitful approach to observe the relationship between the geometries of hydrogen bonds and their dynamics.
    Chemical Physics 12/2013; 427. DOI:10.1016/j.chemphys.2013.10.016 · 2.03 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: To study the structural behavior of brucite at high temperature, we conducted in situ neutron diffraction experiments of a deuterated brucite powder sample, Mg(OD)2, in the temperature range 313–583 K. The sample was stable up to 553 K, above which it started to decompose into periclase (MgO) and D2O vapor. Rietveld analyses of the obtained data were performed using both single-site and three-site split-atom hydrogen models. Our results show that with increasing temperature, unit-cell parameter c increases at a rate ~7.7 times more rapidly than a. This large anisotropy of thermal expansion is primarily due to rapid increase in the interlayer thickness along the c-axis on heating. The amplitudes of thermal vibration for Mg, O, and D increase linearly with increasing temperature; however, the rate of the increase for the lighter D is much larger. In addition, D vibrates anisotropically with a higher magnitude within the (001) plane, as confirmed by our first-principles phonon calculations. On heating, the interatomic distances between a given D and its associated O and D from the adjacent [MgO6] layer increase, whereas the O–D bond length decreases. This behavior suggests weakened D···O and D···D interlayer interactions but strengthened O–D bonding with increasing temperature.
    Physics and Chemistry of Minerals 11/2013; 40(10). DOI:10.1007/s00269-013-0614-4 · 1.40 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Historically spallation target physics and source design have been associated with nuclear physics and engineering. This is because the prediction of spallation target systems performance requires the use of complex particle transport codes like MCNPX [1]. However these codes usually make use of very simple models to describe neutron transport within the materials used. Most often the free gas model and ideal polycrystallinity are assumed. While these models work well to predict epithermal neutron transport and thermalization behavior in large volumes, they have limitations when it comes to the transport of thermal or cold neutrons, particularly in smaller volumes. Over the last decade the LANSCE spallation physics team has extended its traditional spallation physics activities and has incorporated chemistry and material science into spallation target and moderator design. We will show in this article how LANSCE has already benefited from this process and what opportunities exist for further exploitation of material science in target and moderator design.
    Neutron News 10/2013; 24(4):24. DOI:10.1080/10448632.2013.831610
  • Actinides 2013, Karlsruhe, Germany; 07/2013
  • 2013 MRS Spring Meeting, San Francisco CA; 04/2013
  • [Show abstract] [Hide abstract]
    ABSTRACT: Neutron vibrational spectroscopy, together with adsorption isotherm measurements, has been employed to investigate interaction of hydrogen with graphene, hydroxylated graphene, and lithium incorporated graphene. The adsorption studies of hydrogen on these materials indicate varying degrees of hydrogen storage capacity. Graphene is found to have significantly higher hydrogen uptake than graphite and graphite oxide. Neutron vibrational spectroscopy provides direct information concerning hydrogen dynamics including the occurrence of the rotational mode at 119 cm-1; slightly below the free rotor position observed for H2 rotation on graphite. We have also explored how the interaction of hydrogen changes when hydroxyl groups are attached onto the graphene surface and when lithium is incorporated into graphene. The outcome of these studies will also be discussed.
  • [Show abstract] [Hide abstract]
    ABSTRACT: We will discuss the structural and electrochemical characterization of the newly synthesized lithium-rich anti-perovskite, Li3OCl. The crystal structure of this compound was solved using x-ray diffraction techniques, and the electronic and ionic conductivities were measured using electrochemical impedance spectroscopy. This material has an ionic conductivity ranging approximately from 10-4 S/cm to 10-1 S/cm over the temperature range 25^oC to 270^oC (room temperature to just below the melting point). The high ionic conductivity of this lithium-rich electrolyte demonstates strong promise that this material is an ideal candidate for solid state battery applications.
  • [Show abstract] [Hide abstract]
    ABSTRACT: Density Functional Theory (DFT) calculations were performed. They were firstly implemented to optimize the structure and refine the stoichiometry of the only ternary compound, CuLi0.08Mg1.92 of the Cu-Li-Mg system. Furthermore using DFT, several possible structures of CuMg2Hx were optimized. Since most of the hydrides are cubic structures or can be considered as distortions of a cubic structure, we have started calculations for CuMg2Hx (x = 4 - 6) with tetragonal and monoclinic structures, similar to those of the hydrides formed by the nearest neighbors of Cu and Mg in the periodic table: NiMg2H4 and CoMg2H5 (e.g. monoclinic C2/c and tetragonal P4/nmm, respectively). It can be concluded that the most stable configuration corresponds to CuMg2H5 with C2/c structure. We have performed several neutron scattering experiments that are in agreement with the first principles calculations.
    Materials Science Forum 11/2012; 730-732:799-804. DOI:10.4028/www.scientific.net/MSF.730-732.799
  • [Show abstract] [Hide abstract]
    ABSTRACT: Prussian Blue Analogs consists of MC6 and AN6 octahedra connected by cyanide ligands (M, A= metals). They typically crystallize in cubic structures. We have studied temperature and field dependence of the magnetization and the susceptibility of 3d-metal Prussian Blue Analogs, namely the hexacyanocobaltates, -ferrates and -chromates. All compounds exhibit modified Curie --Weiss behavior in the paramagnetic region. The observed effective moments of those compounds were compared with the ones of the respective free-ion values. Furthermore, we find evidence that a few of the compounds exhibit a transition to long-range magnetic order at low temperatures.
  • Source
    M. Hartl, L. Daemen, Guenter Muhrer
    [Show abstract] [Hide abstract]
    ABSTRACT: Over the last three decades water confined in mesoporous silica has been studied extensively. In the vast majority of these studies the water was loaded after the synthesis, which allows the water to be easily released again from the silica at any given time. While this is an advantage for various applications it is a serious disadvantage if considered as a material for neutron moderators. However, if the water is trapped inside the silica during the synthesis this release process is hindered. It is therefore the aim of this paper to investigate water trapped in silica mesospheres during synthesis and to investigate the properties and the structure of the confined water.
    Microporous and Mesoporous Materials 10/2012; 161:7. DOI:10.1016/j.micromeso.2012.04.025 · 3.21 Impact Factor
  • Yusheng Zhao, Luke L Daemen
    [Show abstract] [Hide abstract]
    ABSTRACT: Lithium ion batteries have shown great promise in electrical energy storage with enhanced energy density, power capacity, charge-discharge rates, and cycling lifetimes. However common fluid electrolytes consisting of lithium salts dissolved in solvents are toxic, corrosive, or flammable. Solid electrolytes with superionic conductivity can avoid those shortcomings and work with a metallic lithium anode, thereby allowing much higher energy densities. Here we present a novel class of solid electrolytes with three-dimensional conducting pathways based on lithium-rich anti-perovskites (LiRAP) with ionic conductivity of σ > 10(-3) S/cm at room temperature and activation energy of 0.2-0.3 eV. As temperature approaches the melting point, the ionic conductivity of the anti-perovskites increases to advanced superionic conductivity of σ > 10(-2) S/cm and beyond. The new crystalline materials can be readily manipulated via chemical, electronic, and structural means to boost ionic transport and serve as high-performance solid electrolytes for superionic Li(+) conduction in electrochemistry applications.
    Journal of the American Chemical Society 07/2012; 134(36):15042-7. DOI:10.1021/ja305709z · 11.44 Impact Factor
  • 2012 Plutonium Futures The Science, Cambridge UK; 07/2012

Publication Stats

2k Citations
435.73 Total Impact Points

Institutions

  • 1991–2015
    • Los Alamos National Laboratory
      • • Lujan Neutron Scattering Center
      • • Los Alamos Neutron Science Center
      • • Theoretical Division
      Лос-Аламос, California, United States
  • 2009
    • University of California, Davis
      Davis, California, United States
  • 2007
    • Los Alamos Medical Center
      Los Alamos, New Mexico, United States
  • 1988–1990
    • Purdue University
      • Department of Physics
      ウェストラファイエット, Indiana, United States