118
4 Vibrational Up-Pumping in Some Molecular Energetic Materials
Crystallographic Database (CCDC): β-HMX (Ref: OCHTET15 [34]), α-FOX-7
(Ref: SEDTUQ03 [35]), NTO (Ref: QOYJOD06 [36]), HNB (Ref: HNOBEN [37]),
ABT (EWEYEL [26]), HBT (TIPZAU [28]), TATB (TATNBZ [38]) and TATP
(HMHOCN07 [39]). Optimisation was performed using plane wave DFT as implemented in CASTEP v16 [40]. The electronic wavefunction was expanded in plane
waves to a kinetic energy of 1800 eV for all systems, except HBT (cut-off 1600 eV),
and β-HMX, TATB and TATP (cut-off 1300 eV). Forces were converged to < 5×10
−4
eV/Å, and stresses to < 5 × 10
−4 GPa. The energy change per atom was converged
to < 1 × 10
−9 eV/atom. The resulting unit cell parameters are given in Table 4.2. In
all cases, norm-conserving pseudopotentials were used, as were available within the
CASTEP v16 software package. All phonon calculations were based on the primitive unit cells. Phonon calculations were performed using the linear response method
to calculate the dynamical matrices on a regular grid of wave vectors, and Fourier
interpolated to a fine grid of > 150 points for generation of phonon density of states
(DOS, g(ω)). Phonon dispersion curves were generated by Fourier interpolation of
the computed dynamical matrices along high symmetry paths as proposed by SeeKPath [41] and labelled by IUPAC convention. For TATP, only the zone-centre phonons
were calculated.
Table 4.2 Optimised unit cell parameters for the molecular EMs studied here using the PBE-D2
functional
a/Å
b/Å
c/Å
α/ ◦
β/ ◦
γ / ◦
V/Å 3
dV/%
ABT exp
Pbca
8.352 6.793 11.614 90
90
90
658.962
ABT calc
8.354 6.789 11.618 90
90
90
658.931 −0.004%
HNB exp
C2/c
13.220 9.130 9.680 90
95.500 90
581.490
HNB exp
P(C2/c) 9.046 9.046 9.680 62.280 62.280 60.620 581.492
HNB calc
9.028 9.028 9.771 62.444 62.444 59.981 582.977 +0.26%
β-HMX exp P2 1 /c
6.525 11.024 7.362 90
102.642 90
516.675
β-HMX calc
6.624 11.256 7.373 90
102.222 90
537.299 +4.00%
HBT exp
C2/c
12.401 5.513 9.835 90
115.570 90
606.565
HBT exp
P(C2/c) 6.786 6.786 9.835 113.230 113.230 47.940 303.283
HBT calc
6.706 6.706 9.724 111.837 111.837 49.440 303.075 −0.07%
α-FOX7 exp P2 1 /n
6.934 6.622 11.312 90
90.065 90
519.470
α-FOX7 calc
7.089 6.623 11.440 90
91.273 90
530.898 +2.20%
NTO exp
P-1
5.123 10.314 17.998 106.610 97.810 90.130 902.060
NTO calc
5.159 10.461 17.686 107.247 97.777 90.056 902.450 +0.04%
TATB exp
P-1
9.010 9.028 6.812 108.580 91.820 119.970 442.524
TATB
9.128 9.142 6.767 109.012 92.097 119.936 448.784 +1.41%
TATP exp
P2 1 /c
11.964 14.038 15.595 90
117.270 90
2327.700
TATP calc
11.913 13.811 15.415 90
117.243 90
2255.047 −3.12%
The error in total volume is given with respect to the experimental volume
Low temperature data are used where available
Where conventional cells are non-primitive, the primitive cell is also displayed
4 Vibrational Up-Pumping in Some Molecular Energetic Materials
Crystallographic Database (CCDC): β-HMX (Ref: OCHTET15 [34]), α-FOX-7
(Ref: SEDTUQ03 [35]), NTO (Ref: QOYJOD06 [36]), HNB (Ref: HNOBEN [37]),
ABT (EWEYEL [26]), HBT (TIPZAU [28]), TATB (TATNBZ [38]) and TATP
(HMHOCN07 [39]). Optimisation was performed using plane wave DFT as implemented in CASTEP v16 [40]. The electronic wavefunction was expanded in plane
waves to a kinetic energy of 1800 eV for all systems, except HBT (cut-off 1600 eV),
and β-HMX, TATB and TATP (cut-off 1300 eV). Forces were converged to < 5×10
−4
eV/Å, and stresses to < 5 × 10
−4 GPa. The energy change per atom was converged
to < 1 × 10
−9 eV/atom. The resulting unit cell parameters are given in Table 4.2. In
all cases, norm-conserving pseudopotentials were used, as were available within the
CASTEP v16 software package. All phonon calculations were based on the primitive unit cells. Phonon calculations were performed using the linear response method
to calculate the dynamical matrices on a regular grid of wave vectors, and Fourier
interpolated to a fine grid of > 150 points for generation of phonon density of states
(DOS, g(ω)). Phonon dispersion curves were generated by Fourier interpolation of
the computed dynamical matrices along high symmetry paths as proposed by SeeKPath [41] and labelled by IUPAC convention. For TATP, only the zone-centre phonons
were calculated.
Table 4.2 Optimised unit cell parameters for the molecular EMs studied here using the PBE-D2
functional
a/Å
b/Å
c/Å
α/ ◦
β/ ◦
γ / ◦
V/Å 3
dV/%
ABT exp
Pbca
8.352 6.793 11.614 90
90
90
658.962
ABT calc
8.354 6.789 11.618 90
90
90
658.931 −0.004%
HNB exp
C2/c
13.220 9.130 9.680 90
95.500 90
581.490
HNB exp
P(C2/c) 9.046 9.046 9.680 62.280 62.280 60.620 581.492
HNB calc
9.028 9.028 9.771 62.444 62.444 59.981 582.977 +0.26%
β-HMX exp P2 1 /c
6.525 11.024 7.362 90
102.642 90
516.675
β-HMX calc
6.624 11.256 7.373 90
102.222 90
537.299 +4.00%
HBT exp
C2/c
12.401 5.513 9.835 90
115.570 90
606.565
HBT exp
P(C2/c) 6.786 6.786 9.835 113.230 113.230 47.940 303.283
HBT calc
6.706 6.706 9.724 111.837 111.837 49.440 303.075 −0.07%
α-FOX7 exp P2 1 /n
6.934 6.622 11.312 90
90.065 90
519.470
α-FOX7 calc
7.089 6.623 11.440 90
91.273 90
530.898 +2.20%
NTO exp
P-1
5.123 10.314 17.998 106.610 97.810 90.130 902.060
NTO calc
5.159 10.461 17.686 107.247 97.777 90.056 902.450 +0.04%
TATB exp
P-1
9.010 9.028 6.812 108.580 91.820 119.970 442.524
TATB
9.128 9.142 6.767 109.012 92.097 119.936 448.784 +1.41%
TATP exp
P2 1 /c
11.964 14.038 15.595 90
117.270 90
2327.700
TATP calc
11.913 13.811 15.415 90
117.243 90
2255.047 −3.12%
The error in total volume is given with respect to the experimental volume
Low temperature data are used where available
Where conventional cells are non-primitive, the primitive cell is also displayed