ANSTO :: Browsing by Author "Piltz, RO"

Browsing by Author "Piltz, RO"

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2nd Asia-Oceania Instrument Scientist Workshops, Manly, July 19, 2015
(Taylor & Francis Online, 2015-11-17) Hester, JR; Holt, SA; Imperia, P; Piltz, RO; Rehm, C; Rule, KC; Mole, RA; McIntyre, GJ
No abstract available
The ambiguous origin of thermochromism in molecular crystals of dichalcogenides: chalcogen conds versus dynamic Se−Se/Te−Te bonds
(Wiley, 2023-11-06) Thomas, SP; Singh, A; Grosjean, A; Alhameedi, K; Grønbech, TBE; Piltz, RO; Edwards, AJ; Iversen, BB
We report thermochromism in crystals of diphenyl diselenide (dpdSe) and diphenyl ditelluride (dpdTe), which is at variance with the commonly known mechanisms of thermochromism in molecular crystals. Variable temperature neutron diffraction studies indicated no conformational change, tautomerization or phase transition between 100 K and 295 K. High‐pressure crystallography studies indicated no associated piezochromism in dpdSe and dpdTe crystals. The evolution of the crystal structures and their electronic band structure with pressure and temperature reveal the contributions of intramolecular and intermolecular factors towards the origin of thermochromism—especially the intermolecular Se⋅⋅⋅Se and Te⋅⋅⋅Te chalcogen bonds and torsional modes of vibrations around the dynamic Se−Se and Te−Te bonds. Further, a co‐crystal of dpdSe with iodine (dpdSe‐I2) and an alloy crystal of dpdSe and dpdTe implied a predominantly intramolecular origin of the observed thermochromism associated with vibronic coupling. © 1999-2024 John Wiley & Sons
Chinese puzzle molecule: A 15 hydride, 28 copper atom nanoball
(Wiley Online Library, 2014-05-06) Edwards, AJ; Dhayal, RS; Liao, PK; Liao, JH; Chiang, MH; Piltz, RO; Kahlal, S; Saillard, JY; Liu, CW
The syntheses of the first rhombicuboctahedral copper polyhydride complexes [Cu28(H)15(S2CNR)12]PF6 (NR=NnPr2 or aza-15-crown-5) are reported. These complexes were analyzed by single-crystal X-ray and one by neutron diffraction. The core of each copper hydride nanoparticle comprises one central interstitial hydride and eight outer-triangular-face-capping hydrides. A further six face-truncating hydrides form an unprecedented bridge between the inner and outer copper atom arrays. The irregular inner Cu4 tetrahedron is encapsulated within the Cu24 rhombicuboctahedral cage, which is further enclosed by an array of twelve dithiocarbamate ligands that subtends the truncated octahedron of 24 sulfur atoms, which is concentric with the Cu24 rhombicuboctahedron and Cu4 tetrahedron about the innermost hydride. For these compounds, an intriguing, albeit limited, H2 evolution was observed at room temperature, which is accompanied by formation of the known ion [Cu8(H)(S2CNR)6]+ upon exposure of solutions to sunlight, under mild thermolytic conditions, and on reaction with weak (or strong) acids. © 2014, Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
A combined single crystal neutron/x-ray diffraction and solid-state nuclear magnetic resonance study of the hybrid perovskites CH3NH3PbX3 (X = I, Br and Cl)
(Royal Society of Chemistry, 2015-03-31) Baikie, T; Barrow, NS; Fang, Y; Keenan, PJ; Slater, PR; Piltz, RO; Gutmann, MJ; Mhaisalkara, SG; White, TJ
The 1H and 13C NMR spectra in methylammonium lead halide perovskites, CH3NH3PbX3 (X = I, Br and Cl) show that the CH3NH3+ units undergo dynamic reorientation, as the organic component tumbles in the perovskite cage. In addition, the differences in the anomalously long relaxation times of the protons associated with the CH3 and not the NH3 groups indicate that only the amine end of the CH3NH3+ group is interacting with the inorganic network. Using this information, we have refined some single crystal X-ray and neutron diffraction data to probe their unusual structures in more detail. Furthermore, impedance spectroscopy has been used to monitor the high-temperature phase transition of CH3NH3PbI3, which confirms a significant increase in conductivity, when it is in its high temperature and higher symmetry structural regime. The optical band-gaps of each halide perovskite were determined using UV-visible spectroscopy and are consistent with previous reports. © Royal Society of Chemistry
Combined X-ray and neutron diffraction study of vacancies and disorder in the dimorphic clathrate Ba8Ga16Sn30 of type I and VIII
(Royal Society of Chemistry, 2013-01-01) Christensen, S; Avila, MA; Suekuni, K; Piltz, RO; Takabatake, T; Christensen, M
We report detailed structural investigations of the dimorphic clathrate Ba8Ga16Sn30 that crystallizes in both type I and VIII clathrate structures. Single crystals of type I and VIII have been examined using single crystal X-ray and Laue neutron diffraction in the temperature range T = 10 K-500 K. The utilization of both X-ray and neutron diffraction gives a unique ability to reveal the occurrence of minute vacancy occupancies in the host structure. The vacancies are shown to be located on the 6c (type I) and 24g (type VIII) framework sites. Largest vacancy densities are observed for type I p-Ba8Ga16Sn30, 1.3(4)%, and type VIII n-Ba8Ga16Sn30, 0.7(2)%. The relation between guest atom disorder and occurrence of glasslike thermal conductivity in intermetallic clathrates was also investigated. In type VIII Ba8Ga16Sn30 neither n-type (crystalline thermal conductivity) nor p-type (glasslike thermal conductivity) showed any significant disorder of the guest atoms; they do however show anharmonic motion. The glasslike thermal conductivity of p-type Ba8Ga16Sn30 is interpretable as a result of higher effective mass of p-type charge-carriers affecting phonon scattering. In type I Ba8Ga16Sn30 guest atoms are highly disordered for both carrier types and samples of both charge carrier types have glasslike thermal conductivity. © 2013, Royal Society of Chemistry.
Complex magnetism of quasi-1D maricite-type NaFePO4
(AOCNS 2015, 2015-07-23) Avdeev, M; Piltz, RO; Ling, CD; Auckett, JE; Barpanda, P; Cadogan, JM
We recently reported the magnetic structure of maricite-type NaFePO4 determined using neutron powder diffraction data collected at 3 K1. The crystal structure of this compound is derived from the olivine (Mg2SiO4) type by an ordered distribution of Na and Fe over the two inequivalent Mg sites in the olivine cell. This leads to a magnetically quasi-1D arrangement in which edge-sharing (FeO6) chains are connected to each other only via phosphate groups with a shortest interchain Fe-Fe distance of ~5 Å vs. intrachain distance of ~3.4 Å. Here we report the results of further studies using magnetometry, heat capacity, Mossbauer, and variable field and temperature powder and single crystal neutron diffraction measurements, which reveal not only an intermediate incommensurate magnetic phase existing in zero field within a very narrow interval of ~2 K, but also a metamagnetic transition around 5 T (at 2 K). We will also present and discuss the evolution of the magnetic structure of NaFePO4 as a function of temperature and magnetic field in connection with the crystal structure and compared to that of other maricite type compositions such as AgMnVO42.
Crystal and molecular structure of dichloro(1,10-phenanthroline)dimethyltin(IV), Me2Sn(1,10-phenanthroline)Cl-2, determined by neutron diffraction
(Oldenbourg Wissenschaftsverlag GmbH, 2008-12) Klooster, WT; Piltz, RO; Tiekink, ERT
The tin atom in Me2Sn(phen)Cl-2 is located on a crystallographic site of symmetry m2m and exists within a distorted octahedral geometry defined by a C2Cl2N2 donor set with the tin-bound methyl groups occupying trans- positions. A two-dimensional array stabilised by C-H center dot center dot center dot Cl interactions is established in the crystal structure. Crystal data for Me2Sn(phen)Cl-2: C14H14Cl2N2Sn, M = 399.90, orthorhombic space group Cmcm, a = 11.359(2), b = 18.910(5), c = 7.536(2) angstrom, V = 1618.7(11) angstrom(3), Z = 8, R = 0.073. © 2008, Oldenbourg Wissenschaftsverlag GmbH
Crystal structures of fluorinated aryl biscarbonates and a biscarbamate: a counterpoise between weak intermolecular interactions and molecular symmetry.
(Royal Society of Chemistry, 2011-03-07) Dikundwar, AG; Venkateswarlu, C; Piltz, RO; Chandrasekaran, S; Row, TNG
Conformational features and supramolecular structural organization in three aryl biscarbonates and an aryl biscarbamate with rigid acetylenic unit providing variable spacer lengths have been probed to gain insights into the packing features associated with molecular symmetry and the intermolecular interactions involving ‘organic’ fluorine. Four structures but-2-yne-1,4-diyl bis(2,3,4,5,6-pentafluorophenylcarbonate), 1; but-2-yne-1,4-diyl bis(4-fluorophenylcarbonate), 2; but-2-yne-1,4-diyl bis(2,3,4,5,6-pentafluorophenylcarbamate), 3 and hexa-2,4-diyne-1,6-diyl bis(2,3,4,5,6-pentafluorophenylcarbonate), 4 have been analyzed in this context. Compound 1 adopts a non-centrosymmetric “twisted” (syn) conformation, whereas 2, 3 and 4 acquire a centrosymmetric “extended” (anti) conformation. Weak intermolecular interactions and in particular those involving fluorine are found to dictate this conformational variation in the crystal structure of 1. A single-crystal neutron diffraction study at 90 K was performed on 1 to obtain further insights into these interactions involving ‘organic’ fluorine. © 2011, Royal Society of Chemistry
Crystallographic correlations with anisotropic oxide ion conduction in aluminum-doped neodymium silicate apatite electrolytes
(American Chemical Society, 2013-04-09) An, T; Baikie, T; Wei, FX; Pramana, SS; Schreyer, MK; Piltz, RO; Shin, JF; Wei, J; Slater, PR; White, TJ
To better understand the oxide ion conduction mechanism of rare earth silicate apatites as intermediate temperature electrolytes for solid oxide fuel cells (SOFC), the effect of lower valent metal doping on the performance of Nd(28+x)/3AlxSi6-xO26 (0 <= x <= 2) single crystals has been examined. The measurement of ionic conductivity via AC impedance spectroscopy showed that the conductivities were anisotropic and superior along the c direction. An interesting aspect from the impedance studies was the identification of a second semicircle with capacitance similar to that of a grain boundary component, despite the fact that polarized optical microscopy and electron backscattered diffraction showed that the single crystals consisted of a single grain. This semicircle disappeared after long-term (up to 3 months) annealing of the single crystals at 950 degrees C, also leading to a reduction in the bulk conductivity. In order to explain these observations, single-crystal X-ray diffraction studies were performed both before and after annealing. These studies found the undoped crystal conformed to P6(3)/m, but with the 0(3) oxygen positions, that participate in conduction, split nonstatistically across two sites with a shortened Si-O(3) bond. Consequently, the bond valence sum (BVS) of the Si (4.20) is larger than the formal valence. Fourier difference maps of the Al-doped crystals contain regions of excess scattering, suggesting the possible lowering of symmetry or creation of superstructures. After long-term annealing, the single crystal structure determinations were of higher quality and the experimental and nominal compositions were in better agreement. From these observations, we propose that in the as-prepared single crystals there are regions of high and low interstitial content (e.g., Nd9.67Si6O26.5 and Nd9.33Si6O26), and the second semicircle relates to the interface between such regions. On annealing, Nd redistribution and homogenization removes these interfaces and also reduces the number of interstitial oxide ions, hence eliminating this second semicircle while reducing the bulk conductivity. The results therefore show for the first time that the conductivity of apatite materials containing cation vacancies is affected by the thermal history.© 2013, American Physical Society.
Direct observation of nano-polar-domain phase transition in PLZT ceramics by SANS
(The Bragg Institute, Australian Nuclear Science and Technology Organisation, 2005-11-27) Fei, Y; Piltz, RO; Choy, CL; Lou, HS; Xi, TG; Strunz, P
Small Angle Neutron Scattering (SANS) measurements on Pb(0.92) La(0.08) Zr(0.60) Ti(0.40) O3 (PLZT) ceramics reveals that the ferroelectric phase experiences the evolution into nano-polar-domain (NPD) around the ferroelectric phase transition temperature Tc. This NPD gradually diminished as the temperature increased above the Tc. This director observation gives a strong support on the theory of nanometer-sized polar regions responsible for the extra larger ferroelectric and dielectric constant in this system. © The Authors
Domain structure effects in the relaxor ferroelectric PZN-PT
(Australian Institute of Physics, 2005-01-31) Piltz, RO
PZN-PT (Pb(Zn1/3Nb2/3)O33-x%PbTiO33) exhibits a maximum strain versus electric field exceeding 1% if it is poled along <001 > Two suggestions exist for the origin of this exceptional strain the domain structure created during poling, 'polarisation rotation' due to the existence of a monoclinic phase reported for PZN 8%PT Neutron diffraction data will be presented that shows the monoclmic phase is in fact a distortion of the ambient phase resulting from intersecting domain structures This interpretation also reconciles PZN-4 5%PT which shows similar properties to PZN 8%PT yet does not exist in the monoclmic structure. © 2005 Australian Institute of Physics
Domain structure of 001-Poled PZN-4.5%PT using neutron diffraction
(Taylor & Francis, 2005-09-05) Piltz, RO
The domain structure of PZN-4.5%PT was studied as a function of temperature in an electric field of 500 V/cm applied along 001. The measurements provides direct information on the orientational relationships between the cubic, tetragonal and rhombohedral domains during the field cooling process, and on the volume fraction of domains in each set of orientations. The domains in the tetragonal phase are all related by 90° twins mainly on the (101) and (011) twin planes. The domain structure of the rhombohedral phase agrees with an earlier room temperature and zero field study.
Erratum: Magnetic structure and dzyaloshinskii-moriya interaction in the S=1/2 helical-honeycomb antiferromagnet α−Cu2V2O7 [Phys. Rev. B 92, 024423 (2015)]
(American Physical Society, 2017-03-10) Gitgeatpong, G; Zhao, Y; Avdeev, M; Piltz, RO; Sato, TJ; Matan, K
No abstract available. See the original item at: https://apo.ansto.gov.au/dspace/handle/10238/10250
Experimental and theoretical charge density distribution in two ternary cobalt(III) complexes of aromatic amino acids
(American Chemical Society, 2007-10-11) Overgaard, J; Waller, MP; Piltz, RO; Platts, JA; Emseis, P; Leverett, P; Williams, PA; Hibbs, DE
The experimental charge density distributions in two optically active isomers of a Co complex have been determined. The complexes are Δ-α-[Co(R,R-picchxn)(R-trp)](ClO4)(2)center dot H2O) (1) and Λ-β(1)-[Co(R,R-picchxn)(R-trp)](CF3SO3)(2)) (2), where picchxn is N,N '-bis(2-picolyl-1,2-diaminocyclohexane) and R-trp is the R-tryptophane anion. The molecular geometries of 1 and 2 are distinguished by the presence in complex 1 of intramolecular pi center dot center dot center dot pi stacking interactions and the presence in complex 2 of intramolecular hydrogen bonding. This pair of isomers therefore serves as an excellent model for studying noncovalent interactions and their effects on structure and electron density and the transferability of electron density properties between closely related molecules. For complex 2, a combination of X-ray and neutron diffraction data created the basis for a X-N charge density refinement. A topological analysis of the resulting density distribution using the atoms in molecules methodology is presented along with,d-orbital populations, showing that the metal-ligand bonds are relatively unaltered by the geometry changes between 1 and 2. The experimental density has been supplemented by quantum chemical calculations on the cobalt complex cations: close agreement between theory and experiment is found in all cases. The energetics of the weak interactions are analyzed using both theory and experiment showing excellent quantitative agreement. In particular it is found that both methods correctly predict the stability of 2 over 1. The transferability between isomers of the charge density and derived parameters is investigated and found to be invalid for these structurally related systems. © 2007, American Chemical Society
Finding the Goldilocks zone for chemical crystallography via Laue single-crystal neutron diffraction – what have we learned from KOALA to improve KOALA 2.0?
(International Union of Crystallography, 2021-08-14) Edwards, AJ; Piltz, RO
KOALA is a single-crystal Laue neutron diffractometer standing at the end of guide position of the supermirror guide TG3 at the OPAL reactor, ANSTO. The instrument was initially modelled closely on VIVALDI[1], an instrument available in the user program at the ILL from 2001-2010. The elegantly simple concept of the instrument employs a cylindrical neutron sensitised image plate detector which is used to record a series of diffraction images from a suitable number of crystal positions to provide a sufficient data set from which valid model parameters can be derived to answer questions regarding material properties which cannot be adequately derived from more readily available methods, most particularly X-ray diffraction and more recently the hybrid methodology of quantum crystallography. Our initial practice with the instrument adhered largely to that shared with us by the scientists at the ILL. This early experience[2] was the commencement of a steep learning curve which has, with a very limited number of other instruments brought single-crystal neutron diffraction into greater use in chemistry and chemical crystallography in the second decade of the 21st century. Key developments have been (i) the installation of an Oxford Cryosystems COBRA™ nitrogen cryostream which facilitates handling of oxygen and moisture sensitive compounds (which encompass a significant fraction of the proposals received for the instrument) and (ii) the development of a user accessible data reduction for the diffraction images. From the first proposal round for the instrument in 2009 exciting chemistry was proposed for experiments which exceeded the nominal maximum primitive unit cell volume for the recording of useful diffraction images. A simple work around for this has been to reduce the resolution of the images by manipulation of the temperature at which they are recorded – in order to obtain data against which a model may be refined. More commonly though, it is observed that crystals for which the unit cell volume is relatively large tend, where they can be grown to a size sufficient for Laue neutron diffraction, to have a mosaic spread which limits the resolution of the pattern observed without manipulating the temperature to further reduce the resolution. With careful attention to experimental detail and the availability of discretionary beam-time access it has been possible to undertake studies of important new materials in timeframes which have resulted in the publication of the single-crystal neutron diffraction study with the chemistry it underpins, rather than as a stand alone paper reporting only the neutron study result. It is of particular importance to note that in the case of hydride containing compounds, it can be critical to prove the location of the hydride via neutron diffraction and even a low resolution study can provide the necessary proof. In consequence of their publication with the chemistry, papers from KOALA are now submitted to and published in journals of the highest standing [4-7]. Having achieved a more routine applicability of neutron diffraction in chemical crystallography, we reached a point where electronic components of KOALA had exceeded their serviceable lifespans and contemplation of replacing this aspect of the instrument led us to realise that reworking the existing mechanical elements with new electronics posed significant challenges and would cost a large fraction of the potential cost of building a new instrument. We are fortunate that the decision was reached to design a new instrument which is allowing us to optimise key design elements to yield maximum flexibility of the instrument across all of its possible applications in chemistry, physics, materials science and crystallography. The instrument is currently under construction and should be available for users in the second half of 2022. © The Authors
KOALA 2: implications for magnetic structural and exotic studies
(Australian Nuclear Science and Technology Organisation, 2021-11-24) Piltz, RO
The KOALA single-crystal diffractometer has now been operating for more than a decade and is now nearing retirement (mid-2022). The technical improvements of the new KOALA 2 diffractometer, and the implications for conventional chemical crystallography are described in separate presentations at this meeting. In this presentation we will present the implications for less conventional studies, such as: magnetic structures; incommensurate and other complex structures; very small samples; high-pressure experiments; studies over many temperatures; various preparatory studies of inelastic and diffuse scattering. © The Author
Koala, a versatile single-crystal diffractometer
(Australian Institute of Nuclear Science and Engineering (AINSE), 2020-11-11) Piltz, RO
KOALA is a versatile diffractometer for neutron single-crystal diffraction studies on a wide range of applications in chemistry, materials science and physics. Of the many user experiments published from KOALA data, we present two case studies related to materials science and physics. The S=½ helical-honeycomb antiferromagnet α-Cu2V2O7 shows a broad peak in its magnetic susceptibility ~50 K followed by an abrupt increase below 33 K, indicative of a phase transition to a magnetically ordered state. Neutron diffraction reveals that S=½ Cu2+ spins are antiferromagnetically aligning with an ordered moment of 0.93(9) μB, predominantly along the crystallographic a axis. The photovoltaic materials MAPbX3 (MA = CH3NH3; X = Cl, Br, I) are widely studied due to their high conversion efficiencies. NMR spectra indicates dynamic reorientation of the MA ion, suggesting tumbling within the perovskite cage with only the amine end of the group interacting with the inorganic network. Single-crystal neutron diffraction was used to refinement all three structures for comparison. In each case, the MA group is disordered and surrounded by halogen ions with anisotropic displacement ellipsoids. However, for the Br and Cl structures small anomalies were observed in the probability density of the lead ions, possibly indicating a ferroelectric-like behaviour or a subtle difference in symmetry. © The author.
Magnetic properties of the S = 1/2 antiferromagnetic spin-chain α - Cu2V2O7
(American Physical Society, 2015-03-06) Gitgeatpong, G; Zhao, Y; Avdeev, M; Piltz, RO; Sato, TJ; Matan, K
Magnetic properties of the S = 1 / 2 antiferromagnetic spin-chain, α - Cu2V2O7, have been studied using magnetization and neutron scattering measurements on powder and single-crystal samples. Magnetic susceptibility reveals a Curie-Weiss temperature of Θ = -73.2(9) K with a magnetic phase transition at TN = 33 K while the Bonner-Fisher fit to the magnetic susceptibility for T >TN with magnetic field perpendicular to the crystallographic a - axis yields the intra-chain coupling of |J|/k = 46.0(2) K. Small ferromagnetism below TN is due to spin-canting caused by Dzyaloshinskii-Moriya interactions. Analysis of the neutron diffraction data reveals that the Cu2+ spins are coupled antiferromagnetically along zigzag chains, which run alternately along [011] and [01-1] directions. The ordered moment of 0.925(3) μB is predominantly along the a - axis. Our recent inelastic neutron scattering, which reveals atypical magnetic excitations centered at commensurate wave vectors (0, +/-0.25, 0) around the magnetic zone center, will also be discussed. © 2021 American Physical Society
Magnetic structure and dzyaloshinskii-moriya interaction in the S=12 helical-honeycomb antiferromagnet α−Cu2V2O7
(American Physical Society, 2015-07-23) Gitgeatpong, G; Zhao, Y; Avdeev, M; Piltz, RO; Sato, TJ; Matan, K
Magnetic properties of the S=12 antiferromagnet α−Cu2V2O7 have been studied using magnetization, quantum Monte Carlo (QMC) simulations, and neutron diffraction. Magnetic susceptibility shows a broad peak at ∼50K followed by an abrupt increase indicative of a phase transition to a magnetically ordered state at TN=33.4(1) K. Above TN, a fit to the Curie-Weiss law gives a Curie-Weiss temperature of Θ=−73(1) K suggesting the dominant antiferromagnetic coupling. The result of the QMC calculations on the helical-honeycomb spin network with two antiferromagnetic exchange interactions J1 and J2 provides a better fit to the susceptibility than the previously proposed spin-chain model. Two sets of the coupling parameters J1:J2=1:0.45 with J1=5.79(1) meV and 0.65:1 with J2=6.31(1) meV yield equally good fits down to ∼TN. Below TN, weak ferromagnetism due to spin canting is observed. The canting is caused by the Dzyaloshinskii-Moriya interaction with an estimated bc-plane component |Dp|≃0.14J1. Neutron diffraction reveals that the S=12Cu2+ spins antiferromagnetically align in the Fd′d′2 magnetic space group. The ordered moment of 0.93(9) μB is predominantly along the crystallographic a axis. ©2015 American Physical Society
Molecular origins of the high-performance nonlinear optical susceptibility in a phenolic polyene chromophore: electron density distributions, hydrogen bonding, and ab initio calculations
(American Chemical Society, 2013-05-09) Lin, TC; Cole, JM; Higginbotham, AP; Edwards, AJ; Piltz, RO; Pérez-Moreno, J; Seo, JY; Lee, SC; Clays, K; Kwon, OP
The molecular and supramolecular origins of the superior nonlinear optical (NLO) properties observed in the organic phenolic triene material, OH1 (2-(3-(4-hydroxystyryl)-5,5-dimethylcyclohex-2-enylidene)malononitrile), are presented. The molecular charge-transfer distribution is topographically mapped, demonstrating that a uniformly delocalized passive electronic medium facilitates the charge-transfer between the phenolic electron donor and the cyano electron acceptors which lie at opposite ends of the molecule. Its ability to act as a "push-pull" pi-conjugated molecule is quantified, relative to similar materials, by supporting empirical calculations; these include bond-length alternation and harmonic-oscillator stabilization energy (HOSE) tests. Such tests, together with frontier molecular orbital considerations, reveal that OH1 can exist readily in its aromatic (neutral) or quinoidal (charge-separated) state, thereby overcoming the "nonlinearity-thermal stability trade-off". The HOSE calculation also reveals a correlation between the quinoidal resonance contribution to the overall structure of OH1 and the UV-vis absorption peak wavelength in the wider family of configurationally locked polyene framework materials. Solid-state tensorial coefficients of the molecular dipole, polarizability, and the first hyperpolarizability for OH1 are derived from the first-, second-, and third-order electronic moments of the experimental charge-density distribution. The overall solid-state molecular dipole moment is compared with those from gas-phase calculations, revealing that crystal field effects are very significant in OH1. The solid-state hyperpolarizability derived from this charge-density study affords good agreement with gas-phase calculations as well as optical measurements based on hyper-Rayleigh scattering (HRS) and electric-field-induced second harmonic (EFISH) generation. This lends support to the further use of charge-density studies to calculate solid-state hyperpolarizability coefficients in other organic NLO materials. Finally, this charge-density study is also employed to provide an advanced classification of hydrogen bonds in OH1, which requires more stringent criteria than those from conventional structure analysis. As a result, only the strongest OH center dot center NC interaction is so classified as a true hydrogen bond. Indeed, it is this electrostatic interaction that influences the molecular charge transfer: the other four, weaker, nonbonded contacts nonetheless affect the crystal packing. Overall, the establishment of these structure?property relationships lays a blueprint for designing further, more NLO efficient, materials in this industrially leading organic family of compounds. © 2013, American Chemical Society.

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