Author

# Ulrich Häussermann

Other affiliations: Royal Institute of Technology, Los Alamos National Laboratory, Arizona State University ...read more

Bio: Ulrich Häussermann is an academic researcher from Stockholm University. The author has contributed to research in topics: Crystal structure & Intermetallic. The author has an hindex of 31, co-authored 139 publications receiving 3163 citations. Previous affiliations of Ulrich Häussermann include Royal Institute of Technology & Los Alamos National Laboratory.

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TL;DR: Two highly porous gamma-aluminas, a commercial catalyst obtained from the calcination of boehmite and a highly mesoporous product obtained from amorphous aluminum (oxy)hydroxide via a sol-gel-based approach, are described in this paper.

223 citations

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TL;DR: In this article, the crystal and electronic stucture of the low-temperature polymorph α-Zn4Sb3 has been investigated and it has been shown that during the reversible phase transition, all Zn atoms localize completely and the electronic structure corresponds to that of a narrow-gap semiconductor.

Abstract: β-Zn4Sb3 is an outstanding thermoelectric material mainly due to its extraordinarily low thermal conductivity, which is similar to that of glasses. Recently it was proposed that interstitial Zn atoms are responsible for this peculiar behavior. Here we report on the crystal and electronic stucture of the low-temperature polymorph α-Zn4Sb3. During the reversible phase transition the intricate disorder in β-Zn4Sb3 disappears, and all Zn atoms localize completely. The electronic structure of α-Zn4Sb3 corresponds to that of a narrow-gap semiconductor.

137 citations

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TL;DR: In this article, the authors investigated crystal structure, chemical bonding, and electronic properties of the compounds BiSe, BiSe and BiSe by first-principles calculations within the density functional theory.

Abstract: We have investigated crystal structure, chemical bonding, and electronic properties of the compounds ${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$, BiSe, ${\mathrm{Bi}}_{4}{\mathrm{Se}}_{3}$, and ${\mathrm{Bi}}_{2}\mathrm{Se}$ by first-principles calculations within the density functional theory. The compounds are members of a general series of stacks ${({\mathrm{Bi}}_{2}{\mathrm{Se}}_{3})}_{m}{({\mathrm{Bi}}_{2})}_{n}$ composed of five-layer blocks $\mathrm{Se}\ensuremath{-}\mathrm{Bi}\ensuremath{-}\mathrm{Se}\ensuremath{-}\mathrm{Bi}\ensuremath{-}\mathrm{Se}$ and two-layer blocks $\mathrm{Bi}\ensuremath{-}\mathrm{Bi}$. Both types of blocks can be considered as closed-shell systems. We find that the interaction between two five-layer blocks is of van-der-Waals--type, whereas interactions involving two-layer blocks are of weak covalent nature and stronger. When treating exchange and correlation with the generalized gradient approximation interblock van der Waals bonding is highly underestimated while using the local density approximation yields reasonable results. ${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$, which exclusively consists of five-layer blocks, is a narrow-gap semiconductor, whereas $\mathrm{Bi}\ensuremath{-}\mathrm{Bi}$ blocks containing compounds represent semimetals. Formation energies $m\phantom{\rule{0.3em}{0ex}}{\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}+n\phantom{\rule{0.3em}{0ex}}{\mathrm{Bi}}_{2}={\mathrm{Bi}}_{2m+2n}{\mathrm{Se}}_{3m}$ are close to zero which supports the idea of a potentially continuous series of stacks corresponding to an ordered solid solution of pure Bi in ${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$.

105 citations

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TL;DR: Structural competition in boron group elements has been studied by means of ab initio calculations and an icosahedron based elemental modification higher in energy than the corresponding metallic ground state structures is found for Al and Ga.

Abstract: Structural competition in boron group elements has been studied by means of ab initio calculations. For boron we predict a structural change alpha-B-->alpha-Ga accompanied by a nonmetal-metal transition at a pressure of about 74 GPa. For Al and Ga we find an icosahedron based elemental modification (alpha-B) 0.22 and 0.05 eV/atom, respectively, higher in energy than the corresponding metallic ground state structures. In particular, the low energy difference for Ga raises expectations into the experimental feasibility of new modifications for these elements, especially in nanosized systems.

104 citations

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TL;DR: The origin of the different electronic properties of the intermetallic compounds FeGa3 and RuGa3 was investigated by first-principle calculations in this paper, where it was found that in compounds adopting the FeGa-3 structure type the transition metal atoms and Ga atoms interact strongly.

101 citations

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01 May 1993

TL;DR: Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems.

Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

29,323 citations

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TL;DR: A review of metal hydrides on properties including hydrogen-storage capacity, kinetics, cyclic behavior, toxicity, pressure and thermal response is presented in this article, where a group of Mg-based hydride stand as promising candidate for competitive hydrogen storage with reversible hydrogen capacity up to 7.6 W% for on-board applications.

2,890 citations

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TL;DR: The implementation of various DFT functionals and many‐body techniques within highly efficient, stable, and versatile computer codes, which allow to exploit the potential of modern computer architectures are discussed.

Abstract: During the past decade, computer simulations based on a quantum-mechanical description of the interactions between electrons and between electrons and atomic nuclei have developed an increasingly important impact on solid-state physics and chemistry and on materials science—promoting not only a deeper understanding, but also the possibility to contribute significantly to materials design for future technologies. This development is based on two important columns: (i) The improved description of electronic many-body effects within density-functional theory (DFT) and the upcoming post-DFT methods. (ii) The implementation of the new functionals and many-body techniques within highly efficient, stable, and versatile computer codes, which allow to exploit the potential of modern computer architectures. In this review, I discuss the implementation of various DFT functionals [local-density approximation (LDA), generalized gradient approximation (GGA), meta-GGA, hybrid functional mixing DFT, and exact (Hartree-Fock) exchange] and post-DFT approaches [DFT + U for strong electronic correlations in narrow bands, many-body perturbation theory (GW) for quasiparticle spectra, dynamical correlation effects via the adiabatic-connection fluctuation-dissipation theorem (AC-FDT)] in the Vienna ab initio simulation package VASP. VASP is a plane-wave all-electron code using the projector-augmented wave method to describe the electron-core interaction. The code uses fast iterative techniques for the diagonalization of the DFT Hamiltonian and allows to perform total-energy calculations and structural optimizations for systems with thousands of atoms and ab initio molecular dynamics simulations for ensembles with a few hundred atoms extending over several tens of ps. Applications in many different areas (structure and phase stability, mechanical and dynamical properties, liquids, glasses and quasicrystals, magnetism and magnetic nanostructures, semiconductors and insulators, surfaces, interfaces and thin films, chemical reactions, and catalysis) are reviewed. © 2008 Wiley Periodicals, Inc. J Comput Chem, 2008

2,364 citations

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TL;DR: I. Foldamer Research 3910 A. Backbones Utilizing Bipyridine Segments 3944 1.

Abstract: III. Foldamer Research 3910 A. Overview 3910 B. Motivation 3910 C. Methods 3910 D. General Scope 3912 IV. Peptidomimetic Foldamers 3912 A. The R-Peptide Family 3913 1. Peptoids 3913 2. N,N-Linked Oligoureas 3914 3. Oligopyrrolinones 3915 4. Oxazolidin-2-ones 3916 5. Azatides and Azapeptides 3916 B. The â-Peptide Family 3917 1. â-Peptide Foldamers 3917 2. R-Aminoxy Acids 3937 3. Sulfur-Containing â-Peptide Analogues 3937 4. Hydrazino Peptides 3938 C. The γ-Peptide Family 3938 1. γ-Peptide Foldamers 3938 2. Other Members of the γ-Peptide Family 3941 D. The δ-Peptide Family 3941 1. Alkene-Based δ-Amino Acids 3941 2. Carbopeptoids 3941 V. Single-Stranded Abiotic Foldamers 3944 A. Overview 3944 B. Backbones Utilizing Bipyridine Segments 3944 1. Pyridine−Pyrimidines 3944 2. Pyridine−Pyrimidines with Hydrazal Linkers 3945

1,922 citations

01 Feb 1995

TL;DR: In this paper, the unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio using DFT, MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set.

Abstract: : The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

1,652 citations