Quantum mechanically determined electrostatic potentials for isosurfaces of electron density of a variety of CHNO explosive molecules are analyzed to identify features that are indicative of sensitivity to impact. This paper describes the development of models for prediction of impact sensitivity of CHNO explosives using approximations to the electrostatic potentials at bond midpoints, statistical parameters of these surface potentials, and the generalized interaction properties function [J. S. Murray, T. Brinck, P. Lane, K. Paulsen and P. Politzer, J. Mol. Struct (THEOCHEM) 1994, 307, 55] or calculated heats of detonation. The models are parametrized using a set of 34 polynitroaromatic and benzofuroxan explosives for which impact sensitivity measurements exist. The models are then applied to a test set of 15 CHNO explosives from a variety of chemical families in order to assess the predictive capability of the models. Patterns of the surface potentials of the molecules examined in this study suggest that the level of sensitivity to impact is related to the degree of positive charge buildup over covalent bonds within the inner framework of these explosives. The highly sensitive explosives show large positive charge buildup localized over covalent bonding regions of the molecular structures, whereas the insensitive explosives do not exhibit this feature. For the nitroaromatic and benzofuroxan compounds, sensitivity appears to be related to the degree and distribution of positive charge build-up localized over the aromatic ring or over the C−NO2 bonds.

A quantum mechanically based procedure for estimation of crystal densities of neutral and ionic crystals is presented. In this method, volumes within 0.001 electrons/bohr3 isosurfaces of electron density for the constituent isolated neutral and ionic molecules are calculated to define the molecular volume or formula unit volumes used in predicting the crystal density. The B3LYP density functional theory in conjunction with the 6-31G** basis set were employed to generate the electron densities. The suitability of this method of crystal density prediction was assessed by subjecting a large number (289) of molecular and ionic crystals to the procedure and comparing results with experimental information. The results indicate that, for neutral molecular crystals, the root-mean-square (rms) deviation from experiment is within 4%, whereas the rms deviation is somewhat larger for the 71 ionic crystals evaluated (within 5%).

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In recent years, substantial improvements in the performance of solid propellant guns have resulted from the development of higher energy propellants, higher loading density propellant charge configurations, and propellant geometries and concepts that have provided the progressively increasing gas generation rates required to efficiently use available increases in total energy. Unfortunately, these same features also typically lead to increases in ammunition vulnerability to enemy threats. Coupled with the current interest in much lighter fighting vehicles, the need for ammunition with reduced rather than increased sensitivity is obvious. This report describes the development of a new approach in the U.S. Army to address propellant energy/ performance and sensitivity/vulnerability as a single set of critical design requirements, to be addressed concurrently from the very beginning of the new energetic material research and development cycle. Some elements of this work were presented in abbreviated form at the 19th International Symposium on Ballistics in Interlaken, Switzerland in May 2001 [1]. iii ACKNOWLEDGMENTS The development and execution of a major new thrust such as the Insensitive High Energy Munitions (IHEM) Program involve the contributions of many people at the U.S. Army Research Laboratory (ARL). Acknowledgment is made to Drs. Arpad Juhasz, Thomas Minor, and William Oberle for contributions through the years to high progressivity/high density and in electro-thermal-chemical gun propulsion concepts. The work of Mr. Jerry Watson provided the background for shaped charge jet vulnerability response plot in Figure 11. Dr. Rob Lieb performs mechanical property measurements and interprets their significance. He also performs the microscopic examination of the non-ignited shear-punch samples. Many people are instrumental in conducting the small-scale vulnerability experiments at ARL. Dr. Reed Skaggs is in charge of our battlefield information coordination efforts, Mr. Al Bines and Mr. Bill Sunderland conduct the electric flyer experiments, and Dr. Larry Vande Kieft and Mr. Oliver Blake run the hot fragment conductive ignition and shear-punch experiment. We thank Dr.

Scientific visualization methods have become the new standards for analyzing scientific datasets. However, while these visualization routines provide an excellent qualitative means for data analysis, many researchers still require quantitative information about their data. This paper describes how the marching cubes iso-surface algorithm can be modified to produce not only the qualitative information about the shape of a surface but also some quantitative information regarding the volume of space contained within or beneath that surface. The original marching cubes algorithm decomposes a dataset into cubes based on the grid structure provided. It then searches each cube, determining whether or not the surface intersects that particular cube. During this search, volume calculations can be performed for each cube or partial cube that is contained within or beneath the surface. The results of these calculations can then be summed to obtain a measurement for the volume of space that is within or beneath the surface. These additional tasks can easily be incorporated into the marching cubes algorithm, providing the researcher with a volumetric measurement to support the more qualitative visual information generally produced by an iso-surface algorithm.