Today's research in energetic materials generates tons of new substances, but their properties are almost always missed or incomplete. Sometimes all that you know about interesting compound is it's molecular structure (e.g bond chain and ordering). In order to decide is it worth to spend time and resources on it's synthesis, abilty to predict energetic properties of new compound compound will be very helpful. In general, prediction of properties is a hard work, but can be done even on simple home PC with use of common chemical software. I my post i've tried to show it in most simple, general way, without deep going into special details. Much more detaled information about HEDM properties prediction is avialable in journal articles and quantum chemistry books. Generaly, considering new energetic material we are most interested in four main explosive properties: detonation velocity (this is proportional to substance density and heat of explosion), heat of explosion (this contributes to explosion power), volume of explosion gasses (affects explosive power ant throwing ability) and sensitivity of explosive. All this, except sensitivity can be predicted by means of some chemical calculations, without any experimental data required.

First off all you will need to get some common chemical software, such as molecular structure modeling tools and quantum chemistry package. Some additional visualization and file editing software is usefull as well. Here is a list of programs, witch i found apropriate for our task.

1. Chemoffice Suite. This one is surely familiar to many people who use PC for chemistry. This package contains some general compound modeling tools and some more advanced features, such as rectefication of structure using data from build in compound structure database or simple optimization tools like MM2. Program can also serve as generator of input to further optimization by quantum chemical software. You can review it here: www.cambridgesoft.com/software/ChemOffice/.

2. PC Gamess quantum chemistry package. Surely other quantum chemical codes such as Gaussian, or NWChem can also be used, but Gamess is best in terms of speed and is also free for academic use. PC Gamess is a freely available ab initio and DFT computational chemistry program developed to offer high performance on Intel-compatible x86, AMD64, and EM64T processors. It was initially based on the free GAMESS(US) program sources but extends its functionality in some important areas. The PC GAMESS project is maintained by the staff of the Laboratory of Chemical Cybernetics at Moscow State University (MSU). The project coordinator and leading developer is Dr. Alex A. Granovsky. You can download this package from official server here: http://classic.chem.msu.su/gran/gamess/index.html.

3. In order do calculate substance crystal density using electron density maps provided by PC Gamess, you will need special utility witch i've written specialy for this small article. If you are using Windows XP or later they will run without any setup, if you use other outdated OS you will need VB Runtime Library installed in order to run it. Utility + source code + article from Journal Of Hazardous Materials describing density prediction principle + examples of PC Gamess input & output + Chem3D files used for calculation, can be downloaded in single archive here: http://rapidshare.de/files/40492387/Density_Calc.rar.html

4. To make your work more comfortable and enjoy visualization on the fly you can get some aditional tools such as Chemcraft (visualization tool for PC Gamess and 3D molecular structures), Ultraedit32 file editing tool, capable for fast browsing and editing of big files and FAR file mannager for easy dos style file operations. Chemcraft is shareware, but is fully functional for 30 days after first run, there is also simplified free version avialable. You can get this program here: http://www.chemcraftprog.com.

Then you got essential software, you can beging compound structure modeling. Properties witch we want to calculate are only drop in the ocean, from listed software capabilities, so this programs can be very usefull in many other fields of numerical chemical research.

First of all, you must generate initial molecule structure. To do this launch ChemDraw (2D molecular structue modeling tool from ChemOffice), create a new document and draw your molecule using toolbox at the left side of the screen. Don't worry if your molecule looks asymmetrical or distorted, it can be easily rectified by pressing Clean Up Structure command in Structure menu (watch left picture below). Then your molecule is assembled and rectified in Chemdraw you can transfer it to 3D modeling system of Chem3D. Select your molecule using marquee tool and copy it to clipboard using copy button in edit menu. Now launch Chem3D, create new document and click paste in edit menu, your 2D molecule will be pasted in 3D envouriment (watch middle picture below). To rectify structure in Chem3D and optimize it's steric energy you must use Minimize Energy tool in MM2 menu, that will bring optimization options window, leave all parameters on default and click Run button - this will launch MM2 steric energy minimization. Minimization takes some time, and you will see it's progress as atoms in your model will move arround, untile they settle in energy minimum. Completion of minimization is signaled by word Ready in status bar. Note that optimizer will automatically add lone pairs to several atoms, witch are shown as pink spheres. Rectified 3D structure got from initial one is presented on the right screenshot below:

After MM2 optimizaton your molecule is much closer to real one, but must be further optimized to get valid structure. Final optimization and energy + properties prediction require job of quantum chemical software. Now you must export structure from Chem3D to PC Gamess input file. Chem3D can export PC Gamess input files, however it can't set correct computation options in it, so you must create this file by hand. Gamess input deck require set of all atom coordinates in your molecule, and assumes that molecule is better or less optimized, overvise calculation may not converge. This is a bit of art in providing good initial structure, but one optimized by Chem3D usualy works well. To export file with atom coordinates in format requred by PC Gamess, save file with structure from Chem3D, selecting "Gamess Input" file format. Now our initial structure is complete and we can proceed to PC Gamess quantum chemical calculations.

As you may know, compound's heat of formation is related to structure of compound and is a measure of it's energy, so positions of atoms in molecule relative to each other precisely defines structure energy and dirivated heat of formation value. This is not completely precise, because we take our molecule as single one in free space (igeal gas), but in real crystaline cell molecule is always surrounded by many others and this also affects structure energy. However energy difference done by placing molecule in crystalline cage (heat of vaporisation) is usualy much lower in value then heat of formation, and can be completely skipped if we solve our problem in gas phase aproximation. Heat of formation in solid or liquid state is always lower then one in gas phase, but heat of vaporisation is hard to be predicted due to extreme complexity of calculations needed for it. You should realize that quantum chemestry calculations require a lot of computing power, and ammount of calculations rise dramaticaly then using higher level of theory or growing number of atoms in molecule. In order to compute middle scale HEDM molecule in reasonable time while still getting good quality output property values, we must select computation method very carefully. The most suitable method for our case is semiemperical PM3, witch is fast and good in prediction of geometry and heats of formation. Now we must arrange input file for our job, this file has general structure witch is shown on left picture below.

To give you any idea about what exactly listed parameters do, i give them a short description. First parameter group ($CONTRL) are most importans, as they control the job of PC Gamess program, and designate target of calculation. Our target is specified by keyword "RUNTYP=OPTIMIZE" informing a program that we need to optimize molecule structure and get it's energy, keywords "COORD=CART" and "UNITS= ANGS" set mode of input cordinates to cartesian 3D system using angstrom (10^-10 m) as units of lenth, keywords "SCFTYP=RHF" and "MAXIT=50" forces program to use Restricted Hartree-Fock method to solve Schrodinger equation (core of quantum chemistry theory) for our molecular system and set iteration limiter for it at 50 iterations. $GUESS and $BASIS groups determine choce of initial aproximate orbital primitives, witch will be used for numerical solution of Schrodinger equation in our molecule, more detailed information about basis sets can be found in quantum chemistry literature. $STATPT group controls stationary point search mode. Leave theese all untouched.

Next we have a $DATA group in witch our initial molecule is defined, by provided atom coordinates and core charges. First line below $DATA contains job title witch will be displayed in output file, C1 key defines symetry of our molecule (C1 means no symetry and can be used in any case), lines below contains atom names, core charges and coordinates. Don't worry we not need to calculate them by hand, they are already saved to file by Chem3D program we used before, we just need to copy them to our input file. Contents of file saved by Chem3D is shown in middle picture below. Then editing input file you must ensure that first character on all lines is space and there is line with keyword $END on end of atom coordinate listing. Note that file saved by Chem3D also saves Lp atoms (lone pairs) witch are junk and must be discarded. Result of copy&paste work is complete PC Gamess input file, witch is shown on right picture below:

Once input file is prepared it should be executed by PC Gamess, save input file to directrory where PC Gamess executable is located with name "input", launch comand prompt, navigate to PC Gamess dirrectory and type "pcgamess >pm3.out", this will launch calculations and save results to specified "pm3.out" file. Gamess calculations can take some time, so you can be interested in viewing progress at the moment. To do that you can open "pm3.out" with FAR file viewer tool or by Chemcraft, in file viewer you can monitor calculation process in real time and watch all current actions done by program, Chemcraft will show you 3D structure of your molecule at all optimization steps taken by PC Gamess. All this shown on pictures below:

After execution is complete, you will get both, optimized molecular structure and corresponding heat of formation. To get them open output file "pm3.out" and find line with statement "EQUILIBRIUM GEOMETRY LOCATED", below you will see set of atomic coordinates with optimized molecule structure, corresponding heat of formation is slightly above this line, in the begining of final optimization iteration. You can aslo visualize optimized (real) molecular structure by opening "pm3.out" by Chemcraft and selecting Optimized geometry in the step list. Results of calculations viewed as mentioned above are shown on screenshots below:

As you can see in on the screenshot above, heat of formation of our structure in gas phase is calculated as 40.571 kcal/mol. If you want to convert this value to kJ/mol, you must multiply it by 4.1868, if you want heat of formation in kJ/kg value in kcal/mol must be multiplied by (4.1868*1000/molar mass). Our optimized molecule structure can now be used for calculation of crystal density, we will find it in the next step.

Density is very important for HEDM, because it dirrectly affects detonation velocity. That's why then looking for new effective energetic compounds density is one of the main aims in search, and it very important to have ability to predict it at least aproximately before spending time on synth of new compound. Modern theoretical work on computation of substane crystal density assumes that density is a function of electron density in molecule and that volume of molecule in crystaline cell is proportional to volume of 3D region in witch electron density is above 0.001 electrons per cubic bohr (bohr is unit based on hydrogen electron orbit radius). Electron density map can be computed by means of quantum chemical software, so derived density value can also be determined. PC Gamess can produce electron density map, but it can't calculate volume of reqired zone, this must be done by user or some other external program. Numericaly this task transforms in task of creating isosurface with 0.001 e/bohr3 density value, and calculation of it's inside volume, using electron density values mapped by PC Gamess in set of 3D mesh points. In order to calculate requested volume we should split 3D mesh on cubes, each of those has some volume and electron density values at it's corners. It is clear that if all this values are above 0.001 e/bohr3 our cube is inside isosurface and it's volume must be added to sum, otherwise if values at all corners is below 0.001 e/bohr3 cube is outside isosurface and it's volume is discarded. If values at some corners of cube are bigger then 0.001 and lower then 0.001 at other - this means than isosurface intersects our test cube, cutting off some volume that must be added to sum, this volume can be aproximated by deviding cube volume to 8 parts (number of cube corners) and multiplying this value by number of corners witch have value above 0.001 (e.g number of corners inside isosurface). Because electron density map produced by PC Gamess contains enumorous number of small cubes (millions), volume sum obtainted then considering all this small cubes together will be very precise, but will also require some intense calculations, fortunately we are not forced to do this by hand, this is PC live for. I've written small utility witch will do this operation using PC Gamess generated density map, so our job is launch games electron mapping job and to open resulted output file by utility. Typical electron density mapping job input file is shown on left picture below, lines with atomic cordinates are missed and should be filled with coordinates of our previous optimization run, witch we done then predicting heat of formation. After copy&paste work we will get input file like one shown on right picture below:

Before processing this new input file we must clean up PC Gamess directory from output generated from previous job, otherwise this data could be overwritten and PC Gamess execution will terminate with warning about old output file existance. Make a new folder inside PC Gamess one, and move old "input" and "punch" files to this folder. Now you can save new "input" file in PC Gamess folder, and execute it as in previous run, using command prompt and typing "pcgamess >dens.out". I you examing new input file closely you will note that this time we used another basis set, and used RUNTYP=ENERGY, theese are changed because PC Gamess can not generate electron density maps using PM3 and other semiemperical basis sets, however to prevent computation of new molecular structure we used single point energy run, in witch structure of our molecule will be preserved. After execution of our mapping job is completed we can open output files to watch obtained results, electron density map, in witch we are interested is located in file called "punch" inside PC Gamess dirrectory. This file contains many other information, and our map is located under $CUBE group and it's end is marked be $END keyword, as shown on screens below:

Now we can use produced electron density map to estimate crystal density of our compound. To do this just open it with utility i've provided, type path to PUNCH file and click Load File button. Remember that utility recognizes only CHNO substances, and will fail if substance contain other elements or if input file format is incorrect, so be sure to supply correct input file. Results of this operation are shown on screenshot below:

As you can see on this screenshot, calculated crystal density of our compound is 1.896 g/cm3. However this value must be corrected by multiplying it with 0.955 witch is correction factor for our basis set (PM3), introduced because calculated density produced by this basis set is systematically higher then real. So for our compound we estimate density of 1.896*0.955 = 1.81 g/cm3, that is very close to experimental value 1.82 g/cm3. If you want to visualize your resulting density map by Chemcraft, or to use it for input in some other programs, you can convert it to CUB file format. This is easily done by copying all data between $CUBE and corresponding $END group in "punch" file and saving it a new file with .CUB extention. This file can be visualized by Chemcraft program, density isosurface drawn by chemcraft and part of this exported .CUB file are shown on the screens below:

Heat of explosion determines, how much energy is released then our substance detonate. As you may know heat generated from rection is sum of formation heats of explosion products, subtracted by heat of formation of initial compound. To calculate heat of explosion we must assume some detonation equation, revealing products of detonation process and their proportions against each other. Generaly detonation can be assumed as simple burning process, in witch carbon inside explosive compound is oxidized to CO2, hydrogen to H2O and nitrogen to N2, by using oxygen contained inside explosive molecule. But how can we be then oxygen contained in molecule present in larger or smaller ammount then required to get only this products? Then there is too many oxygen in molecule we must assume that excess oxygen is released in free state (O2), if there is not enough oxygen for full oxidation situation is bit more complicated and we must take to account atom oxidation "priority". Hydrogen gets oxidized on first place, and oxygen will be used to form H2O until all hydrogen atoms will be oxidized, and only then oxygen will be used to oxidize carbon backbone, free hydrogen is released in explosion only if there is not enougth oxygen in initial molecule to fully oxidize is (for example in HN3 explosion). Carbon is first oxidized to carbon monixide CO, CO2 will form only if there is enough oxygen remaining, to form CO and CO2 mixture, and only CO2 if oxygen content is enough for full oxidation. Free carbon can be released only then not enough oxygen remaining to convert all carbon atoms to CO, and will be released in mixture with CO if oxygen content of explosive is too low. This model is reasonably simpified, but can be used for getting some usefull information about properties of explosive. Four our case (RDX, C3N6H6O6) we can assume following decomposition equation:

Heat of formation of initial explosive compound is already known from calculation and to get heat of explosion we need to know heats of formation of explosion products. These can be calculated in same way by using PM3 method in PC Gamess, and are precalculated as (also in kcal/mol): CO = -19,74453 ; H2O = -53,42649 ; CO2 = -85,03881 ; N2 = 17,56604 ; O2 = -21,42657. Using this value and molecular mass of our compound we can calculate heat of explosion in several units:

Minus sign means that heat is released (exotermic reaction). This value is lower then experimental (-5297 kJ/kG) by about 1400 kJ/kg. Our result is inaccurate because experimental heat is taken using solid compound (and we assumed gas state reaction) and also because heat of formation depends from temperature whitch is not same as room temperature used then computing our heat of formation values, simplified detonation equation also takes part in this inaccuracy. While resulted value is not very precise, it still very usefull, because it can be used to compare different energetic molecules with each other, taking to account the fact that real heats of explosion have same proportions to each other as calculated ones if compound is of the same class. For example, we know experimental and calculated heats of explosion for compound A, and for compound B of same class we know only calculated heat of explosion, we can use this data to get real heat of explosion for compound B: Acalc/Bcalc = Areal/Breal ; Breal = Areal*Bcalc/Acalc.

Detonation equation witch we assumed above can also be used to calculate explosion gas volume, that is important factor contributing to power of our explosive. As you can see in decomposition equation above 1 mol of our compound (RDX) generates 9 mol of gaseous products. Taking to account the fact that 1 mol of any ideal gas at room temperature is 22.4 liters, we can calculate volume of explosion gases:

Calculated value is very close to experimental (908 l/kg), so volume of explosion products can be predicted quite accurately, if explosion detonation equation is composed correctly. You may heard about Trauzl bomb test for explosives, it measures expansion power of explosion gases, and depends only from heat of explosion and explosion gas volume. This value can aslo be derivated using parameters we calculated above, but has no much interest for us.

Detonation velocity is one of the main factors, determining power of explosive. The detonation velocity is the rate of propagation of a detonation in an explosive; if the density of the explosive is at its maximum value, and if the explosive is charged into columns which are considerably wider than the critical diameter, the detonation velocity is a characteristic of each individual explosive and is not influenced by external factors. It decreases with decreasing density of packing in the column. The standard hydrodynamic theory used for computing VOD of an explosive is concerned only with the amount of energy liberated and the nature of end products, and is independent of chemical reactions. The density, heat of formation and atomic composition can be integrated into an empirical formula for predicting performance of a proposed explosive.

There are many different relations describing dependence of detonation velocity from explosive constitution, and they use different parameters witch are used for velocity estimation, however most common are explosive constitution, heat of formation, oxygen balance and of course density. Formulas have different degree in accuracy and often give good estimations for some class of explosive compounds, while giving prediction with less accuracy for another compound classes. In our case we are interested in ones, witch give reasonably good predictions for any compound class, and use computationaly available parameters. It should be noted that in many formulas detonation velocity is much more dependent on constitution of explosive, then from heat of formation, and inaccurate heats of formation got from calculations (gas phase value, not taking to account crystalline energy effects) are perfectly suitable for prediction of detonation velocity. In reverse to heat of formation, density greatly affects detonation velocity and is one of the main factors controlling it, good thing is that computed densities are precise enough to perform good estimations of detonation velocity.

Now, I will show you how to use two different sets of empirical formulas to estimate detonation velocity and detonation pressure. First formula, having more simple nature, was described by Aisenshtadt in Russian explosive material journal, it can be used to estimate detonation velocity from heat of formation, explosive constitution and oxygen balance:

At this formula Hf is heat of formation in kcal/mol, Mw is a molecular mass of explosive compound in g/mol, p is explosive density in g/cm3, D1.6 is detonation velocity in km/sec at 1.6 g/cm3 and Dp is detonation velocity at target density (p) it is also in km/sec. Use of this formula is pretty straight forward, just use your explosive formula, predicted heat of formation and select density you want to use in calculation, but don’t forget to convert your heat of formation into kcal/mol, before substitution to formula. Example results for our calculated molecule (RDX) are shown below:

C3H6O6N6 ; Hf= 40.571 kcal/mol ; r = 1.8 g/cm3 ; B = ((3 + 6 + 6 + 6)/222.117)*1000 = 94.544 ; OB = |16(6-6-3)/222.117|*100 = 21.610 ; Qv = - |(40.571 + 0.3(6+6+6))/222.117| * 1000 = -206.964 ; M = 3 ; D1.6 = (0.73*94.544 – 0.24*21.610 + 0.0073*206.964)^0.5 = 8.083 km/sec ; D1.8 = 8.083 + 3(1.8-1.6) = 8.683 km/sec.

Note, that in formula above B is factor dependent from substance constitution, OB is form of oxygen balance, and Qv is approximate heat of explosion. All this are multiplied by coefficients got by fitting experimental data for many explosive compounds, and all this values are finally united then completing detonation velocity. This is a philosophy of empirical formulas – select properties witch as we think are determining value being estimated, and then fit experimental data to get coefficients for estimated value formula. Formula above can also be used for mixtures of explosives, in this case explosive formula and heat of formation must be substituted by corresponding average values for explosive mixture. As you can see calculated detonation velocity is pretty close to experimental (8.750 km/sec), error is only 0.75%. Divergence can vary for different classed of compounds, but formula usually give satisfactory results.

To give an alternative to Aisenshtadt formula, i will also show usage of formulas proposed by M.H. Keshavarz (References: Propellants, Explosives, Pyrotechnics 30 (2005), No. 2 ; Predicting the Detonation Velocity of CHNO Explosives by a Simple Method ; pp 105-108 and Journal of Hazardous Materials A119 (2005) 25–29 ; Simple determination of performance of explosives without using any experimental data). This formula uses calculated gas phase heat of formation (calculated in same way as we done – by PM3 method) of explosive compound instead of experimental one, and volume of explosion gasses derivated from estimated explosive detonation equation. Method assumes that all heat generated by explosion is used to heat explosion products, that allows to estimate explosion temperature witch is then used in pair with explosion gas volume and density to estimate detonation velocity. Estimation of explosion temperature is bit of art in numerical way, and requires some math operations or numerical analysis. To estimate explosion we must use heat balance for our process, but we can’t simply use standard heats of formation of explosion products as we done then estimating heat of explosion, method requires to take account to temperature dependence of heat of formation in explosion products. Heat of formation is function of temperature, exact equation for this dependence can be obtained from isobaric heat capacity vs temperature dependency, this one is usually approximated in polynomial form as shown on illustration below. Heat of formation vs temperature function is obtained by integration of this dependency, as shown below:

Cp is heat capacity at constant pressure ; Hf are heats of formation ; T is temperature ; Nj is number of moles of product j in detonation equation ; A,B,C,D,E,F are constants for each individual compound obtained by fitting experimental heat capacity data. Equation at the bottom of illustration above is heat balance equation, showing that all heat released by explosion is used entirely to heat explosion product (adiabatic explosion), since explosion process is extremely fast, adiabatic assumption is pretty much accurate. To solve heat balance equation we can use simple numerical method called bisection.

Bisection method is a root-finding algorithm which repeatedly divides an interval in half and then selects the subinterval in which a root exists. Suppose we want to solve the equation f(x) = 0. Given two points a and b such that f(a) and f(b) have opposite signs, we know by the intermediate value theorem that f must have at least one root in the interval [a, b] as long as f is continuous on this interval. The bisection method divides the interval in two by computing c = (a+b) / 2. There are now two possibilities: either f(a) and f(c) have opposite signs, or f(c) and f(b) have opposite signs. The bisection algorithm is then applied recursively to the sub-interval where the sign change occurs (watch illustration below).

To solve our heat balance, first we must transform our heat balance equation to form suitable for bisection f(x)=0, next we reasonably assume that explosion temperature lies somewhere between room temperature and some high temperature for example 6000K. Now we are ready to solve our problem, we just need to get coefficients from explosion equation (Nj’s), coefficients got by fitting experimental heat capacity (A, B, C, D, E, F) and heat of formation of our explosive witch we calculated before. Be aware that these experimental coefficients are calculated to fit heat equation then T/1000 is used instead of simple temperature value, so to get correct results you must place T/1000 in place of T in equation below.

C3N6H6O6 = 3H2O + 3CO + 3N2

For example i will show single calculation of f(T) at T=600K, so you can see how data listed above is working in our equation. Be careful, heat balance root finding takes a lot of simple calculations, be sure to make no errors in signs, numbers and choose proper temperature intervals in table, or you will get completely confusing results. Here is an example, i’ve mentioned:

Root bracketing is now straight forward, bisection method is stable and usually converges quite fast. Method is the same as in bisection method description, but f(x) is replaced with our function f(T), results are shown in table below. As you can see method converged to temperature about 3731K witch is our explosion temperature. Amount of calculations is too big to by hand, that’s why i’ve written utility for calculation of detonation parameters, PC must pay by fair work for money you spent on it.

Now, then temperature of explosion and volume of explosive gasses is known, we can simply calculate corresponding detonation velocity, by means of simple formula shown below. In formula (r) is density at witch detonation velocity is being predicted (g/cm3), Texp is temperature of explosion in K found in calculations above, (n) is a amount of gas generated by 1 gram of explosive (simple sum of mole numbers of explosion products in right side of detonation equation, divided by molecular weight of our explosive, value in mol/g), resulting detonation velocity will be in km/sec.

Substitution of our data (T=3731K, p = 1.8 g/cm3; n = 9/222.11 mol/g) we get detonation velocity of 8899 m/sec, experimental value at 1.8 g/cm3 is 8750 m/sec. So found detonation velocity is slightly overestimated, error is 1.67%, so accuracy is also very good, especialy taking to account the fact that when we started we known absolutely nothing about our compound! Formula works well on many classes of explosive, but requires some intense calculations.

Now we have predicted velocity witch is quite precise, but one may also want to predict detonation pressure, fortunately it’s very easy as it can be predicted using only heat of formation and explosive composition, as shown in another M.H Keshavarz article. Formula for calculation of detonation pressure is shown below:

Here Hf is explosive heat of formation (we already calculated it way before), r is density in g/cm3, Mw is molecular mass of our explosive, resulted detonation pressure will be in kbar. Using data for our explosive (a=3, b=6, c=6, d=6, Hf=169.86 kJ/mol, r=1.8 g/cm3) we can calculate detonation pressure for our explosive, witch is 414 kbar (experimental is 341 kbar) with 18% error, however with no surprise due to gas phase calculated heat of formation, instead of crystalline experimental one. On experimental heat of formation formula gives much more precise result (355 kbar calculated vs 341 kbar measured).

In total, from zero knowledge starting point we have predicted: heat of formation, crystal density, volume of explosion gasses, detonation temperature, detonation pressure, detonation velocity. Of course there are many other estimation methods, but this ones are simple and can be made at home. For convenience i have written small utility witch calculates estimated parameters using methods described above and in references mentioned. Utility requires VB runtime libraries, but if you use windows XP it should run without any setup. Utility with the source code + references for this article in small archive file are attached to this post, screenshot is shown below: