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924 results on '"Ernst, Christian"'

4. Einleitung

Author

Ernst, Christian, Neuber, Nils, Series editor, Krüger, Michael, Series editor, and Ernst, Christian

Published
2018
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12. Teilkostenrechnung

Author

Ernst, Christian, Schenk, Gerald, Schuster, Peter, Schuster, Peter, Series editor, Ernst, Christian, and Schenk, Gerald

Published
2017
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13. Ausblick

Author

Ernst, Christian, Schenk, Gerald, Schuster, Peter, Schuster, Peter, Series editor, Ernst, Christian, and Schenk, Gerald

Published
2017
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14. Plankostenrechnung

Author

Ernst, Christian, Schenk, Gerald, Schuster, Peter, Schuster, Peter, Series editor, Ernst, Christian, and Schenk, Gerald

Published
2017
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16. Einführung

Author

Ernst, Christian, Schenk, Gerald, Schuster, Peter, Schuster, Peter, Series editor, Ernst, Christian, and Schenk, Gerald

Published
2017
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24. Insensitive high explosives: IV. Nitroguanidine – Initiation & detonation

Author

Ernst-Christian Koch

Subjects
Military Science
Abstract

This paper reviews the detonative properties of low bulk density (LBD), high bulk density (HBD) Nitroguanidine (NGu)(1), CAS-No: [556-88-7] and 82 explosive formulations based on NGu reported in the public domain. To rank the performance of those formulations they are compared with 15 reference compositions containing both standard high explosives such as octogen (HMX)(2), hexogen (RDX)(3), pentaerythritol tetranitrate (PETN)(4), 2,4,6-trinitrotoluene (TNT)(5) as well as insensitive high explosives such as 3-nitro-1,2,4-triazolone (NTO)(6), 1,3,5-triamino-2,4,6-trinitrobenzene (TATB)(7), 1,1-diamino-2,2-dinitroethylene (FOX-7)(8) and N-Guanylurea dinitramide (FOX 12)(9). NGu based formulations are superior to those based on FOX-12 or TATB and are a close match with FOX-7 based explosives, the latter just having higher Gurney Energies (∼10%) and slightly higher detonation pressure (+2%). NGu based explosives even reach up to 78% of the detonation pressure, 82% Gurney energy and up to 95% of detonation velocity of HMX. LBD-NGu dissolves in many melt cast eutectics forming dense charges thereby eliminating the need for costly High Bulk Density NGu. Nitroguanidine based formulations are at the rock bottom of sensitiveness among all the above-mentioned explosives which contributes to the safety of these formulations. The review gives 132 references to the public domain. For a review on the synthesis spectroscopy and sensitiveness of Nitroguanidine see Ref. [1]. Keywords: Cook-off, Detonation, Insensitive munitions, Nitroguanidine, Shock sensitvity

Published
2019
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25. Special materials in pyrotechnics VII: Pyrotechnics used in thermal batteries

Author

Ernst-Christian Koch

Subjects
Military Science
Abstract

Thermal batteries are unique direct current (DC) electrical power sources with long shelf live, high reliability and higher power density than classical alkaline batteries. This paper gives a brief overview into the working principle of thermal batteries and reviews the properties of zirconium/barium chromate (Zr/BaCrO4) pyrolant previously used as first fire and iron/potassium perchlorate (Fe/KClO4) pyrolant (Heat), commonly applied as heating pellet in thermal batteries and its hazard properties. The review gives 64 references to the public domain. CAS-Nos. Zr: [7440-67-7], BaCrO4: [10294-40-3], Fe: [7439-89-6], KClO4: [7778-74-7], Viton: [9011-17-0].CAS-Nos. Zr: [7440-67-7], BaCrO4: [10294-40-3], Fe: [7439-89-6], KClO4: [7778-74-7], Viton: [9011-17-0]. Keywords: Barium chromate, Heat-powder, Iron, Lithium, Molten salt, Potassium perchlorate, Pyrotechnics, Thermal battery, Zirconium

Published
2019
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30. Local embedded-fragment methods for excited states in periodic systems

Author

Flach, Ernst-Christian, Usvyat, Denis, Maschio, Lorenzo, and Römelt, Michael

Subjects
Point Defects, F-center in MgO, Periodic Systems, Excited States, Quantum Chemistry, Lokale Korrelationsmethoden, Periodische Systeme, Angeregte Zustände, Punktdefekte, Farbzentren in MgO, Quantenchemie, Fragment-basierte Verfahren, Local Correlated Wavefunction Methods, 541 Physikalische Chemie, ddc:541, Embedding Techniques
Abstract

Ein fragment-basierter Ansatz zur Berechnung von vertikalen Anregungsenergien in periodischen Systemen wurde entwickelt. Das Ziel war eine wellenfunktions-basierte Hierarchie von lokalen post-Hartree-Fock Methoden, welche über das weitverbreitete Ein-Elektronen Bild der Bandlücke hinausgehen und eine Möglichkeit zur systematischen Verbesserung der Ergebnisse liefern. Darüber hinaus sollte durch die Verwendung von lokalen Orbitalen eine nahtlose Einbettung des Fragments ermöglicht und eine effektive Methode für die Untersuchung von Defekten in periodischen Systemen geschaffen werden. Als erster Schritt wird das fragment-basierte Configuration Interaction Singles (CIS) Model vorgestellt. Im Anschluss erfolgt der Wechsel zum fragment-basierten lokalen algebraic-diagrammatic construction Modells zweiter Ordnung (DF-LADC(2)). Beide Methoden wurden für ein neutrales Farbzentrum in Magnesiumoxid (MgO) getestet. Dabei wurden Fragmente mit bis zu 57 Atomen verwendet. Eine Konvergenz mit der Fragmentgröße, der Größe der Superzellen und des K-mesh konnte erreicht werden. Dennoch wurde eine erste Anregungsenergie von 5.9 eV erhalten, was 0.9 eV über dem veröffentlichten experimentellen Wert liegt. Mit hoher Wahrscheinlichkeit rührt die Abweichung vom Basissatzvollständigkeitsfehler her. ”Finite-Cluster”-Berechnungen bestätigen entsprechende Basissatzfehler. Interessanterweise stimmt die erste Anregungsenergie für ein Oberflächenfarbzentrum in MgO mit einigen experimentellen Werten überein. Allerdings decken die experimentellen Werte für diese Systeme einen weiten Bereich ab (1.15 - 4.2 eV)., An embedded-fragment approach for calculation of vertical excitation energies in periodic systems has been developed. The aim is a wave-function-based hierarchy of local post-Hartree-Fock models, which goes beyond the very common one-electron picture of the band gap and offers a way for systematic improvability of the results. The use of local occupied and virtual orbitals allows for a seamless embedding model for the fragment and becomes especially effective in studying defects in solids. As a first step in the hierarchy an embedded-fragment Configuration Interaction Singles (CIS) model is presented. The second step is an embedded-fragment local algebraic diagrammatic construction scheme of second order (DF-LADC(2)). Both methods are tested for an neutral color center in bulk and surface magnesium oxide (MgO). Different fragments with up to 57 atoms were studied. A convergence with fragment size, super-cell size and k-mesh has been achieved. However a first excitation energy of 5.9 eV is obtained for the bulk MgO, which is 0.9 eV above the reported experimental value. The deviation most likely originates from the basis set incompleteness error, which, according to finite cluster studies, can be sizable. Interestingly for a surface color center in MgO the observed first excitation energy of 4.1 eV agrees with some of the experimental values (4.2 eV). However for the surface color centers in MgO the scatter of the experimental results is very large (1.15 eV - 4.2 eV).

Published
2023

43. Kontrollrechnungen

Author

Ernst, Christian, Riegler, Christian, Schenk, Gerald, Ernst, Christian, Riegler, Christian, and Schenk, Gerald

Published
2014
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