An Effect of Hydrostatic Compression on Defects in Energetic Materials: AB Initio Modeling Maija

1998 ◽  
Vol 538 ◽  
Author(s):  
M. Kuklja ◽  
A. Barry Kunz
Keyword(s):  
Band Gap ◽  
Edge Dislocation ◽  
Hot Spots ◽  
Energetic Materials ◽  
Electronic Excitation ◽  
First Principle ◽  
Molecular Dissociation ◽  
External Hydrostatic Pressure ◽  
Pressure Changes ◽  
Favorable Conditions

AbstractFirst-principle theoretical investigation of the basic defects such as a molecular vacancy, a vacancy dimer, an edge dislocation, and a micro-crack in organic explosive molecular crystals is presented. As an example we considered solid RDX (C3H6N6O6) which is well studied unstable solid. It was established that external hydrostatic pressure changes optical properties of defect-free RDX as well as of the crystal with defects narrowing the band gap. The lattice defects (especially dislocations) are identified with the so-called “hot spots.” The nature of local electronic states introduced in the band gap by the edge dislocation and formed mainly by molecular orbitals of N-NO2 group is analyzed. Favorable conditions for molecular dissociation due to electronic excitation are shown.

scholarly journals Properties of Novel Non-Silicon Materials for Photovoltaic Applications: A First-Principle Insight

Materials ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2006 ◽  
Author(s):  
Murugesan Rasukkannu ◽  
Dhayalan Velauthapillai ◽  
Federico Bianchini ◽  
Ponniah Vajeeston
Keyword(s):  
Band Gap ◽  
Density Functional ◽  
Crystalline Silicon ◽  
Visible Region ◽  
Initial Population ◽  
First Principle ◽  
Direct Band Gap ◽  
Depth Analysis ◽  
Photovoltaic Applications ◽  
Direct Band

Due to the low absorption coefficients of crystalline silicon-based solar cells, researchers have focused on non-silicon semiconductors with direct band gaps for the development of novel photovoltaic devices. In this study, we use density functional theory to model the electronic structure of a large database of candidates to identify materials with ideal properties for photovoltaic applications. The first screening is operated at the GGA level to select only materials with a sufficiently small direct band gap. We extracted twenty-seven candidates from an initial population of thousands, exhibiting GGA band gap in the range 0.5–1 eV. More accurate calculations using a hybrid functional were performed on this subset. Based on this, we present a detailed first-principle investigation of the four optimal compounds, namely, TlBiS2, Ba3BiN, Ag2BaS2, and ZrSO. The direct band gap of these materials is between 1.1 and 2.26 eV. In the visible region, the absorption peaks that appear in the optical spectra for these compounds indicate high absorption intensity. Furthermore, we have investigated the structural and mechanical stability of these compounds and calculated electron effective masses. Based on in-depth analysis, we have identified TlBiS2, Ba3BiN, Ag2BaS2, and ZrSO as very promising candidates for photovoltaic applications.

Atomistic Calculations of Dopant Binding Energies in ZnGeP2

1997 ◽  
Vol 484 ◽  
Author(s):  
Ravindra Pandey ◽  
Melvin C. Ohmer ◽  
A. Costales ◽  
J. M. Recio
Keyword(s):  
Experimental Data ◽  
Band Gap ◽  
Interatomic Potential ◽  
Host Lattice ◽  
Binding Energies ◽  
First Principle ◽  
Atomistic Model ◽  
Group Iii ◽  
Atomistic Calculations

AbstractAtomistic model has been applied to study various cation dopants, namely Cu, Ag, B, Al, Ga and In in ZnGeP2. The pairwise interatomic potential terms representing the interaction of dopants with the host lattice ions are derived using first principle methods. Defect calculations based on Mott-Littleton methodology predict small binding energies for Cu and Ag substituting Zn in the lattice which are in agreement with the available experimental data. The group III dopants (i.e. B, Al, Ga and In) at the Ge site are predicted to have large binding energies for a hole except B which shows a distinct behavior. This may be due to large mismatch in atomic sizes of B and Ge. At the Zn site, the calculated binding energies of the group III dopants place donor levels in the middle of the band gap.

Modification on TiO2-a Photosensitive Material

2013 ◽  
Vol 579-580 ◽  
pp. 148-152
Author(s):  
Miao Sun ◽  
Yong Hu ◽  
Hua Guo
Keyword(s):  
Density Functional Theory ◽  
Band Gap ◽  
Light Absorption ◽  
Potential Application ◽  
Density Functional ◽  
First Principle ◽  
Functional Theory ◽  
Photosensitive Material ◽  
The Past ◽  
Light Area

TiO2, as photosensitive materials, has attracted much attention owing to its potential application in the solution of environmental pollution during the past decades. Four doped TiO2systems were constructed and studied by using the first principle based Density Functional Theory .The results indicate that P-doped and N-doped TiO2all have better light absorption in the visible light area than pristine TiO2although the band gap of N-doped system reduced less. However, the band gap of F-doped and Cl-doped TiO2increase a little, which causing the absorption to decrease. We suggest from the results that the P atom and N atom are valuable in the modification of TiO2.

Classical versus ab initio structural relaxation: electronic excitations and optical properties of Ge nanocrystals embedded in a SiC matrix

2004 ◽  
Vol 832 ◽  
Author(s):  
Giancarlo Cappellini ◽  
H.-Ch. Weissker ◽  
D. De Salvator ◽  
J. Furthmüller ◽  
F. Bechstedt ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Optical Properties ◽  
Ab Initio ◽  
First Principles ◽  
Electronic Excitation ◽  
First Principle ◽  
Electronic Excitations ◽  
Combined Method ◽  
Classical Molecular Dynamics ◽  
Ge Nanocrystals

ABSTRACTWe discuss and test a combined method to efficiently perform ground- and excited-state calculations for relaxed structures using both a quantum first-principles approach and a classical molecular-dynamics scheme. We apply this method to calculate the ground state, the optical properties, and the electronic excitations of Ge nanoparticles embedded in a cubic SiC matrix. Classical molecular dynamics is used to relax the large-supercell system. First-principles quantum techniques are then used to calculate the electronic structure and, in turn, the electronic excitation and optical properties. The proposed procedure is tested with data resulting from a full first-principles scheme. The agreement is quantitatively discussed between the results after the two computational paths with respect to the structure, the optical properties, and the electronic excitations. The combined method is shown to be applicable to embedded nanocrystals in large simulation cells for which the first-principle treatment of the ionic relaxation is presently out of reach, whereas the electronic, optical and excitation properties can already be obtained ab initio. The errors incurred from the relaxed structure are found to be non-negligible but controllable.

Hot Spot Histories in Energetic Materials

1992 ◽  
Vol 296 ◽  
Author(s):  
A. M. Mellor ◽  
D. A. Wiegand ◽  
K. B. Isom
Keyword(s):  
Hot Spots ◽  
Energetic Materials ◽  
Ignition Temperature ◽  
Hot Spot ◽  
Original Form ◽  
Independent Variables ◽  
Shock Impact ◽  
Similarities And Differences ◽  
Hot Spot Formation ◽  
Spot Formation

AbstractInterest in the mechanisms by which hot spots either grow to sustained reaction or are quenched results from the observation that the energy required to ignite a propellant or explosive can be significantly less than that needed to bulk heat a test specimen uniformly to its ignition temperature. This result is independent of the original form of non-thermal energy and has been used to interpret data for shock, impact, friction and electrostatic discharge (ESD) stimuli. We present new flowcharts which include 1) events resulting in hot spot formation and 2) subsequent pathways which lead to sustained reaction or quenching. The mechanism appears capable of categorizing and demonstrating the similarities and differences between hot spot growth or quenching, for impact and ESD stimuli. Sample confinement and temperature and stimulus duration are the independent variables whose roles are particularly clarified in the mechanism.

Molecular Composition, Structure, and Sensitivity of Explosives

1992 ◽  
Vol 296 ◽  
Author(s):  
Carlyle B. Storm ◽  
James R. Travis
Keyword(s):  
Molecular Structure ◽  
Hot Spots ◽  
Energetic Materials ◽  
Physical State ◽  
Hot Spot ◽  
Energetic Material ◽  
Specific Situation ◽  
Reaction Products ◽  
Ambient Conditions ◽  
Delayed Reaction

AbstractHigh explosives, blasting agents, propellants, and pyrotechnics are all metastable relative to reaction products and are termed energetic materials. They are thermodynamically unstable but the kinetics of decomposition at ambient conditions are sufficiently slow that they can be handled safely under controlled conditions. The ease with which an energetic material can be caused to undergo a violent reaction or detonation is called its sensitivity. Sensitivity tests for energetic materials are aimed at defining the response of the material to a specific situation, usually prompt shock initiation or a delayed reaction in an accident. The observed response is always due to a combination of the physical state and the molecular structure of the material. Modeling of any initiation process must consider both factors. The physical state of the material determines how and where the energy is deposited in the material. The molecular structure in the solid state determines the mechanism of decomposition of the material and the rate of energy release. Slower inherent reaction chemistry leads to longer reaction zones in detonation and inherently safer materials. Slower chemistry also requires hot spots involved in initiation to be hotter and to survive for longer periods of time. High thermal conductivity also leads to quenching of small hot spots and makes a material more difficult to initiate. Early endothermic decomposition chemistry also delays initiation by delaying heat release to support hot spot growth. The growth to violent reaction or detonation also depends on the nature of the early reaction products. If chemical intermediates are produced that drive further accelerating autocatalytic decomposition the initiation will grow rapidly to a violent reaction.

Hot spots in energetic materials generated by infrared and ultrasound, detected by thermal imaging microscopy

2014 ◽  
Vol 85 (2) ◽  
pp. 023705 ◽  
Author(s):  
Ming-Wei Chen ◽  
Sizhu You ◽  
Kenneth S. Suslick ◽  
Dana D. Dlott
Keyword(s):  
Thermal Imaging ◽  
Hot Spots ◽  
Energetic Materials

Electronic and dielectric properties of silicene functionalized with monomers, dimers and trimers of B, C and N atoms

RSC Advances ◽  
2014 ◽  
Vol 4 (60) ◽  
pp. 31700-31705 ◽  
Author(s):  
Brij Mohan ◽  
Ashok Kumar ◽  
P. K. Ahluwalia
Keyword(s):  
Dielectric Properties ◽  
Band Gap ◽  
First Principle ◽  
First Principle Calculations ◽  
Gap Opening ◽  
C And N

First principle calculations have been performed to study the geometric, electronic and dielectric properties of low-buckled silicene with the adsorption of monomers, dimers and trimers of B, C and N atoms. A band gap opening has been achieved for all the C adsorbates, homo dimers of B and N, the hetero N–B dimer and the B–C–N trimer on silicene.

Sign in / Sign up

Export Citation Format

Share Document