Anthony M Reilly

Fritz Haber Institute of the Max Planck Society, Berlín, Berlin, Germany

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Publications (25)171.73 Total impact

  • Anthony M Reilly, Alexandre Tkatchenko
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    ABSTRACT: Aspirin has been used and studied for over a century but has only recently been shown to have an additional polymorphic form, known as form II. Since the two observed solid forms of aspirin are degenerate in terms of lattice energy, kinetic effects have been suggested to determine the metastability of the less abundant form II. Here, first-principles calculations provide an alternative explanation based on free-energy differences at room temperature. The explicit consideration of many-body van der Waals interactions in the free energy demonstrates that the stability of the most abundant form of aspirin is due to a subtle coupling between collective electronic fluctuations and quantized lattice vibrations. In addition, a systematic analysis of the elastic properties of the two forms of aspirin rules out mechanical instability of form II as making it metastable.
    Physical Review Letters 08/2014; 113(5):055701. · 7.73 Impact Factor
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    ABSTRACT: An accurate determination of the electron correlation energy is an essential prerequisite for describing the structure, stability, and function in a wide variety of systems. Therefore, the development of efficient approaches for the calculation of the correlation energy (and hence the dispersion energy as well) is essential and such methods can be coupled with many density-functional approximations, local methods for the electron correlation energy, and even interatomic force fields. In this work, we build upon the previously developed many-body dispersion (MBD) framework, which is intimately linked to the random-phase approximation for the correlation energy. We separate the correlation energy into short-range contributions that are modeled by semi-local functionals and long-range contributions that are calculated by mapping the complex all-electron problem onto a set of atomic response functions coupled in the dipole approximation. We propose an effective range-separation of the coupling between the atomic response functions that extends the already broad applicability of the MBD method to non-metallic materials with highly anisotropic responses, such as layered nanostructures. Application to a variety of high-quality benchmark datasets illustrates the accuracy and applicability of the improved MBD approach, which offers the prospect of first-principles modeling of large structurally complex systems with an accurate description of the long-range correlation energy.
    The Journal of Chemical Physics 05/2014; 140(18):18A508. · 3.12 Impact Factor
  • Anthony M Reilly, Alexandre Tkatchenko
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    ABSTRACT: The development and application of computational methods for studying molecular crystals, particularly density-functional theory (DFT), is a large and ever-growing field, driven by their numerous applications. Here we expand on our recent study of the importance of many-body van der Waals interactions in molecular crystals [A. M. Reilly and A. Tkatchenko, J. Phys. Chem. Lett. 4, 1028 (2013)], with a larger database of 23 molecular crystals. Particular attention has been paid to the role of the vibrational contributions that are required to compare experiment sublimation enthalpies with calculated lattice energies, employing both phonon calculations and experimental heat-capacity data to provide harmonic and anharmonic estimates of the vibrational contributions. Exact exchange, which is rarely considered in DFT studies of molecular crystals, is shown to have a significant contribution to lattice energies, systematically improving agreement between theory and experiment. When the vibrational and exact-exchange contributions are coupled with a many-body approach to dispersion, DFT yields a mean absolute error (3.92 kJ/mol) within the coveted "chemical accuracy" target (4.2 kJ/mol). The role of many-body dispersion for structures has also been investigated for a subset of the database, showing good performance compared to X-ray and neutron diffraction crystal structures. The results show that the approach employed here can reach the demanding accuracy of crystal-structure prediction and organic material design with minimal empiricism.
    The Journal of Chemical Physics 07/2013; 139(2):024705. · 3.12 Impact Factor
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    ABSTRACT: Molecular crystals: The structures and relative energies of glycine polymorphs are determined using dispersion corrections to PBE and PBEh density functionals. The picture shows a potential-energy surface for the a-b plane of γ-glycine obtained with density functional theory including many-body dispersion interactions.
    Angewandte Chemie International Edition 05/2013; · 11.34 Impact Factor
  • Anthony M. Reilly, Alexandre Tkatchenko
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    ABSTRACT: The near endless possibilities for assembling molecular materials has long posed a difficult challenge for theory. All crystal-structure prediction methods acknowledge the crucial contribution of van der Waals or dispersion interactions, but few go beyond a pairwise additive description of dispersion, ignoring its many-body nature. Here we use two databases to show how a many-body approach to dispersion can seamlessly model both solid and gas-phase interactions within the coveted “chemical accuracy” benchmark, while the underlying pairwise approach fails for solid-state interactions due to the absence of many-body polarization and energy contributions. Our results show that recently developed methods that treat the truly collective nature of dispersion interactions are able to reach the accuracy required for predicting molecular materials, when coupled with nonempirical density functionals.
    Journal of Physical Chemistry Letters 03/2013; 4(6):1028–1033. · 6.59 Impact Factor
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    ABSTRACT: Standard semilocal and hybrid density functionals are widely used for studying cohesive properties of covalent, metallic, and ionic materials. Only recently it has been recognized that long-range van der Waals (vdW) interactions, that are missing in all semilocal and hybrid functionals, are important for an accurate description of cohesion in solids. Here we construct a database of 64 solids where reference cohesive properties are obtained from a critical revision of the available experimental data. All-electron DFT calculations with explicit treatment of zero-point vibrations for all cohesive properties are performed using the LDA, PBE, and the empirical meta-GGA M06-L [1] functionals. For 23 semiconductors, we carry out PBE and M06-L calculations with the inclusion of screened long-range vdW energy [2]. We find that PBE is the most systematic from the three employed functionals, and its accuracy is improved by a factor of two after the inclusion of vdW interactions. The LDA functional considerably overbinds for all the studied solids. The M06-L functional describes middle-range correlation better for certain semiconductors and ionic crystals, but fails for heavier semiconductors and metals.[4pt] [1] Zhao and Truhlar, JCP (2006).[0pt] [2] Tkatchenko, DiStasio, Car, Scheffler, PRL (2012).
    03/2013;
  • Anthony Reilly, Alexandre Tkatchenko
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    ABSTRACT: While dispersion interactions are known to be essential to the stability and accurate prediction of molecular-crystal structures, the vast majority of computational methods use simple pairwise approximations to model these interactions, ignoring the non-additive, many-body nature of long-range electron correlation. Here we use the recently developed many-body dispersion (MBD) method (PRL 108, 236402; PNAS 109, 14791) together with a representative database of molecular crystals, to illustrate how important electrodynamic screening and many-body contributions are to crystal stability. Crucially, these MBD contributions allow DFT calculations to reach the highly coveted ``chemical accuracy'' with respect to high-level calculations and experiments in both the crystalline and gaseous phases. This ability to treat molecular solids and their components on such an accurate and equal footing is essential for controled and informed design of complex materials.
    03/2013;
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    ABSTRACT: The benefits of combining experimental and computational methods have been demonstrated by a study of the dynamics and solid‐state structure of α‐benzophenone. Dispersion‐corrected and ‐uncorrected density functional theory molecular dynamics simulations were used to obtain displacement parameters, with the dispersion‐corrected simulations showing good agreement with the experimental neutron and X‐ray diffraction values. At 70 K, quantum‐nuclear effects resulted in poor values for the hydrogen atoms, but the heavy‐atom values still show excellent agreement, suggesting that molecular dynamics simulations can be a useful tool for determining displacement parameters where experimental data are poor or limited.
    Journal of Applied Crystallography 01/2013; 46(3). · 3.34 Impact Factor
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    ABSTRACT: We show that electrodynamic dipolar interactions, responsible for long-range fluctuations in matter, play a significant role in the stability of molecular crystals. Density functional theory calculations with van der Waals interactions determined from a semilocal "atom-in-a-molecule" model result in a large overestimation of the dielectric constants and sublimation enthalpies for polyacene crystals from naphthalene to pentacene, whereas an accurate treatment of non-local electrodynamic response leads to an agreement with the measured values for both quantities. Our findings suggest that collective response effects play a substantial role not only for optical excitations, but also for cohesive properties of non-covalently bound molecular crystals.
    Physical review. B, Condensed matter 11/2012; 87(6). · 3.77 Impact Factor
  • Anthony M. Reilly, Heiko Briesen
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    ABSTRACT: The crystal growth from solution of a fcc LJ system has been studied using a kMC model based on MD-derived rate constants. While classifying the surface states based solely on the number of nearest neighbors limits the model to qualitative insights, a number of approximations employed in previous kMC simulations of Kossel-type lattices have been found to be unsuitable for the current system. This likely stems form the integration-controlled nature of the growth in the MD simulations. Using both “direct” and supersaturation scaled MD-derived rate constants, the kMC simulations have been used to explore growth at high and low temperatures, revealing non-linear growth behavior at low temperatures that could not be seen on the MD timescale.
    Journal of Crystal Growth 09/2012; 354(1):34–43. · 1.55 Impact Factor
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    Anthony M Reilly, Heiko Briesen
    The Journal of Chemical Physics 08/2012; 137(5):059901. · 3.12 Impact Factor
  • Maximilian Greiner, Anthony M Reilly, Heiko Briesen
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    ABSTRACT: Using molecular-dynamics (MD) simulations the densities and self-diffusion coefficients of a range of liquid monoacid triacylglycerides (TAGs) have been studied as a function of temperature and, for the first time, pressure. While offset by their ambient properties, the response of the TAGs to temperature and pressure is qualitatively similar. Application of pressure was found to significantly increase densities and reduce diffusion of the TAG molecules, suggesting that it may have as much a role in processing and crystallizing TAGs as supercooling does. A solution of glycerol tripalmitate and glycerol trihexanoate was also studied, showing that application of pressure should lead to a significant decrease in the saturation point of the solution, which is an important consideration for processing TAGs. Different solid/liquid interfaces of glycerol tripalmitate have also been investigated. Although crystal growth could not be observed, dissolution of one interface was seen in the MD simulations. The results suggest that over moderate distances the melting of TAGs may be cooperative in nature, rather than involving dissolution of individual TAG molecules.
    Journal of Agricultural and Food Chemistry 04/2012; 60(20):5243-9. · 2.91 Impact Factor
  • Anthony M Reilly, Heiko Briesen
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    ABSTRACT: The feasibility of using the molecular dynamics (MD) simulation technique to study crystal growth from solution quantitatively, as well as to obtain transition rate constants, has been studied. The dynamics of an interface between a solution of Lennard-Jones particles and the (100) face of an fcc lattice comprised of solute particles have been studied using MD simulations, showing that MD is, in principle, capable of following growth behavior over large supersaturation and temperature ranges. Using transition state theory, and a nearest-neighbor approximation growth and dissolution rate constants have been extracted from equilibrium MD simulations at a variety of temperatures. The temperature dependence of the rates agrees well with the expected transition state theory behavior.
    The Journal of Chemical Physics 01/2012; 136(3):034704. · 3.12 Impact Factor
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    ABSTRACT: Two new anharmonic forms for the Debye-Waller factor, aimed at modelling curvilinear and asymmetric motion, have been introduced. These forms permit the refinement of structures with these types of anharmonic motion using a small number of additional parameters. Molecular-dynamics-derived numerical probability density functions (PDFs) have been used to assess the merit of these new functions in real space. The comparison is favourable particularly for the curvilinear PDF based on a parabolic coordinate system change of a trivariate Gaussian distribution. The initial results also suggest that high-order even terms from the Gram-Charlier series may be important for modelling methyl-group libration. The molecular-dynamics data sets provide useful insights into the nature of anharmonic thermal motion. Addressing the problem in real space allows intuitive PDFs to be developed but numerical methods may be necessary for these methods to be implemented in refinement programs as an analytical Debye-Waller factor cannot always be obtained.
    Acta crystallographica. Section A, Foundations of crystallography 07/2011; 67(Pt 4):346-56. · 49.93 Impact Factor
  • Anthony M Reilly, Carole A Morrison, David W H Rankin
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    ABSTRACT: Molecular-dynamics-derived numerical probability density functions (PDFs) have been used to illustrate the effect of different models for thermal motion on the parameters refined in a crystal structure determination. Specifically, anharmonic curved or asymmetric PDFs have been modelled using the traditional harmonic approximation and the anharmonic Gram-Charlier series treatment. The results show that in cases of extreme anharmonicity the mean and covariance matrix of the harmonic treatment can deviate significantly from physically meaningful values. The use of a Gram-Charlier anharmonic PDF gives means and covariance matrices closer to the true (numerically determined) anharmonic values. The physical significance of the maxima of the anharmonic distributions (the most probable or mode positions) is also discussed. As the data sets used for the modelling process are theoretical in origin, these most probable positions can be compared to equilibrium positions that represent the system at the bottom of its potential-energy surface. The two types of position differ significantly in some cases but the most probable position is still worthy of report in crystal structure determinations.
    Acta crystallographica. Section A, Foundations of crystallography 07/2011; 67(Pt 4):336-45. · 49.93 Impact Factor
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    ABSTRACT: A new, readily tractable route to determining short-range order models for materials exhibiting occupational disorder and diffuse scattering using first-principles solid-state quantum mechanical calculations is presented and illustrated with application to the disordered, layered molecular material phloroglucinol dihydrate.
    Crystal Growth & Design. 04/2011; 11(6).
  • Carole A Morrison, Anthony M Reilly
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    ABSTRACT: We present an ab initio molecular dynamics study of the iron triad complex (PH(3))(3)MH(4), (M = Os, Ru and Fe). We calculate numerical atomic probability density functions (PDFs), which offer direct visualisation of the degree of anharmonicity present in these complexes. Fitting our calculated PDFs to a parabolic transformation of the standard crystallographic ellipsoidal PDF allowed the bond correction for librational motion observed in the M-H distances to be obtained. For the Ru and Fe complexes we also attempt to quantify the bond distance correction needed to describe the eta(2)-bound H(2) ligand anharmonically. From our simulations we also obtain anharmonic vibrational spectra, which we compare to experimental data. Finally, we also comment on a spontaneous H(2)/(H)(2) ligand flipping process observed for the Fe complex.
    Dalton Transactions 06/2010; 39(23):5527-34. · 3.81 Impact Factor
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    ABSTRACT: Path-integral molecular dynamics have been used to simulate the phase-I crystalline form of ammonia, using an empirical force field. This method allows quantum-mechanical effects on the average geometry and vibrational quantities to be evaluated. When these are used to adjust the output of a high-temperature density functional theory simulation, the results are consistent with those given by the most recent structural refinement based on powder neutron diffraction data. It is clear that the original refinement overestimated thermal motion, and therefore also overestimated the equilibrium N-{H/D} bond length.
    The Journal of Chemical Physics 04/2010; 132(13):134511. · 3.12 Impact Factor
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    ABSTRACT: Path-integral molecular dynamics (PIMD) simulations with an empirical interaction potential have been used to determine the experimental equilibrium structure of solid nitromethane at 4.2 and 15 K. By comparing the time-averaged molecular structure determined in a PIMD simulation to the calculated minimum-energy (zero-temperature) molecular structure, we have derived structural corrections that describe the effects of thermal motion. These corrections were subsequently used to determine the equilibrium structure of nitromethane from the experimental time-averaged structure. We find that the corrections to the intramolecular and intermolecular bond distances, as well as to the torsion angles, are quite significant, particularly for those atoms participating in the anharmonic motion of the methyl group. Our results demonstrate that simple harmonic models of thermal motion may not be sufficiently accurate, even at low temperatures, while molecular simulations employing more realistic potential-energy surfaces can provide important insight into the role and magnitude of anharmonic atomic motions.
    The Journal of Chemical Physics 03/2010; 132(9):094502. · 3.12 Impact Factor
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    ABSTRACT: The equilibrium molecular structure of the decasilsesquioxane, Si(10)O(15)H(10), in the gas phase has been determined by gas electron diffraction. Molecular dynamics calculations were used to give amplitudes of vibration and differences between interatomic distances in the equilibrium structure and the vibrationally averaged distances that are given directly by the diffraction data. The molecules have D(5h) symmetry, and do not show the distortions that are apparent in the crystalline phase. The ten-membered silicon-oxygen rings are found to be particularly flexible in the gas phase, a phenomenon that was also seen in crystal structures. The Si-O bond lengths in the ten-membered rings are 161.6(2) pm long and in the eight-membered rings they are 162.2(3) pm, with Si-O-Si angles of 155.0(5) and 153.9(7) degrees , respectively.
    Dalton Transactions 10/2009; · 3.81 Impact Factor

Publication Stats

33 Citations
171.73 Total Impact Points

Institutions

  • 2012–2014
    • Fritz Haber Institute of the Max Planck Society
      Berlín, Berlin, Germany
    • Technische Universität München
      • Department for Process Engineering
      München, Bavaria, Germany
  • 2013
    • University of Texas at Austin
      • Institute for Computational Engineering and Sciences
      Austin, TX, United States
  • 2007–2011
    • The University of Edinburgh
      • School of Chemistry
      Edinburgh, SCT, United Kingdom