Energetic materials (EM) act as the key chemical activity component in weapon systems, and energetic crystals are the main and functional part therein. Until now, the most widely used energetic crystals have been molecular crystals, including TNT, RDX, HMX, and TATB. The thermal properties, mechanical properties, and chemical reactivity of energetic molecular crystals are of great importance for a whole EM. The classic forcefields (FF) are still useful for typical energetic crystals—i.e., even though they generally have simple potential functions, the accuracy can be ensured by refitting for specific compound.
FFs | Valence Terms | van der Waals Interaction Term |
Electrostatic Interaction Term | Applications | |||||
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SRT [1] | SRT [20] | \ | Buckingham 6-exp form | Coulomb function | RDX HMX CL-20 FOX-7 PETN (lattice parameter, density, mechanics) |
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SAPT [19] | SAPT [38] | \ | Buckingham 6-exp form | Simplified Coulomb function | FOX-7 (thermal properties, pressure responses, isothermo) | ||||
SRT-AMBER [13] | SRT-AMBER [32] | Harmonic bond stretching, harmonic angle bending, cosine torsion term | Buckingham 6-exp form | Coulomb function | RDX (lattice parameter, density, melting point, mechanics) TNAZ (lattice parameter, density, melting point) |
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SB [8] | SB [27] | Harmonic bond term, angle term, dihedral term, anharmonic torsion term | Buckingham form | Coulomb function | RDX HMX CL-20 (shock compression, shear bands, elastic constants and modulus) |
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Boyd’s [15] | Boyd’s [34] | Bond stretching described by Morse function, angle bending described by harmonic function | Buckingham LJ 6-12 form | Coulomb function | RDX (lattice parameter, density, thermodynamics, vibration spectra, thermal expansion, mechanics) | ||||
NETMFF [21] | NETMFF [40] | Bond term, angle term, dihedral (torsion angle) term, out-of-plane bending angle term, cross-coupling terms of bond–bond, bond–angle couplings | Damped Buckingham form | Coulomb function | RDX (lattice parameter, density, thermal expansion) | ||||
GRBF [16] | GRBF [35] | Harmonic bond stretch term, bond-angle bend term, dihedral angle torsion term | Lennard–Jones 12-6 form | Coulomb function | TATB (lattice parameters, density, thermal expansion, isotherm) | ||||
Bedrov’s [17] | Bedrov’s [36] | Harmonic functions of covalent bonds, three-center bends, and improper dihedrals | Buckingham 6-exp form | Coulomb function | TATB (lattice parameter, thermal expansion, mechanics, vibration spectra, thermal conductivity) | ||||
Neyertz’s [20] | Neyertz’s [39] | Angle-bending deformations described by harmonic function, torsional motions around the dihedral angles τ, sp | 2 | ring and NO | 2 | structures kept planar described by harmonic function | Lenard-Jones 12-6 form | Coulomb function | TNT DNT (lattice parameter, density, tensile, bulk and shear modulus) |
Dreiding [22] | Dreiding [41] | Bond stretching interaction term, angle bending interaction term, dihedral angle interaction term, inversion interaction term | Lennard–Jones 12-6 form | Coulomb function | TATB (geometries, crystal packing, thermal expansion) | ||||
OPLS-AA [24] | OPLS-AA [43] | Bond term, angle term, dihedral term | Lennard–Jones 12-6 form | Coulomb function | CL-20 (lattice parameter, density, polymorph prediction) |