Computational approaches to heats of formation

摘要: Heats of formation are significant practical importance in thermochemistry general. Because experimental values available for less than 0.1% the more ten million compounds known, considerable effort has been expended upon developing computational approaches. The use density functional and high-level ab initio procedures to calculate ∆H f , which shall be focus this chapter, increasing steadily recent years, despite demands that they (especially ) place computer resources. While limitations molecular size continue exist, although much so techniques, it is becoming ever feasible compute heats with well-accuracy a variety systems area energetic materials. Within functional/ framework, several different approaches have used find . These described chapter. There description methodologies— functional, /empirical functional/empirical combinations—liquid solid phase formation, applications discussion on boron aluminum combustion products H/C/N/O/F compounds. An interesting trend concerns effect substituting NF 2 (difluoramine) group NO It likely produce higher density, larger number moles gaseous per gram compound efficient ignition/combustion boron- aluminum-based propellant formulations. For molecules interest large Gn (Gaussian-n) or CBS (complete basis set) methodology, two discussed viable options, do occasionally relatively errors. Appropriate homodesmic reactions, if possible, can useful alternative, better yet, serve as check, provided required (gas) known sufficient accuracy.