First-Principle Studies on the Pressure-Induced Structural Changes in

Article pubs.acs.org/JPCC

First-Principle Studies on the Pressure-Induced Structural Changes in Energetic Ionic Salt 3‑Azido-1,2,4-triazolium Nitrate Crystal Yan Liu,† Li Zhang,‡ Guixiang Wang,† Lianjun Wang,*,†,‡ and Xuedong Gong*,† †

School of Chemical Engineering, Nanjing University of Science and Technology, Nanjing 210094, Jiangsu, P. R. China School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Nanjing 210094, Jiangsu, P. R. China

‡

ABSTRACT: Periodic first-principle calculations have been performed to study the effect of high pressure on the geometrical and electronic structures of the energetic ionic salt 3-azido-1,2,4-triazolium nitrate (ATAN) under hydrostatic pressure of 0−300 GPa. The local density approximation with CA-PZ functional has been adopted because the crystal structure optimized with it agrees better with the experimental results than with other functionals at the ambient pressure. When the hydrostatic compression is exerted upon the ATAN crystal, the unit cell parameters, density, total energy, interatomic distances, bond angles, atom charges, bond populations, band structure, and density of states of ATAN crystal change regularly with the increase in pressure except at 200 GPa where the structural transformations occur. Although the azido group bends gradually and slowly to form a five-membered tetrazole ring, the H atom in the adjacent cation transfer to the terminal N atom of the azido group and a new covalent bond forms at 200 GPa; thus, the azide−tetrazole ring−chain transformation has not completely been realized even under the higher pressure owing to this new covalent bond. nature.29 It is a strong enough base to form perchlorate and nitrate salts.30 For energetic materials, high velocity shockwaves can result in very high pressure, about 50 GPa,31,32 in the explosive detonation process. Hence, information about their structures at high pressures is required to better understand the physical and chemical properties, as well as performance of explosives.33,34 Actually, high-pressure technology has been applied extensively to study various materials such as metals, semiconductors, superconductors, minerals, pharmaceutical compounds, energetic materials, etc.35,36 Two general high-pressure experimental methods are dynamic shockwave and direct static compression.37 The influences of dynamic and static pressures are inequable; for example, hexahydro-1,3,5-trinitro-1,3,5-s-triazine (RDX), an important explosive, can bear 65.5 GPa from the static pressure,38 while shockwave with 2.5 GPa will initiate the plastic explosive containing 91% RDX by weight.39 As compared with dynamic method, static compression combined with high-pressure spectroscopic and diffraction techniques40−46 can accurately determine the crystal structure of materials under extreme conditions and provide direct information about equations of state, variations in lattice parameters, molecular structure, polymorphs, and the response of intermolecular interactions to pressure.

1. INTRODUCTION Energetic materials have been extensively used for both military and civilian purposes.1−4 In order to meet the challenging requirements of improving the performance of existing products, many new energetic materials have been designed and synthesized. In recent years, energetic ionic salts attract considerable attention because they possess many advantages over traditional molecular energetic compounds. For example, they tend to exhibit lower vapor pressures, essentially eliminating the risk of exposure through inhalation, and higher densities, advantageous for detonation properties, than their atomically similar nonionic analogues.5−8 Nitrogen-containing heterocycles are one of the important sources of energetic salts. They usually have higher heats of formation, density, heats of reaction, and oxygen balance compared to those of their carbocyclic analogues. Heterocyclic rings, whose hydrogen atoms have been substituted by amino, nitro, or azide substituents to improve their detonation properties, can pair with anions such as nitrate, perchlorate, dinitramide, and so on to form highly energetic salts. In addition, because a higher percentage of the decomposition products is dinitrogen, these energetic ionic salts except perchlorate are more environmentally acceptable.5,6,9,10 Azoles, the five-membered nitrogen-containing heterocycles, are excellent ions for energetic salts. A large number of azolebased energetic salts have been synthesized and investigated,11−19 especially the 1,2,4-triazole series.20−29 Among them, 3-azido-1,2,4-triazole has been used as a precursor to some energetic materials, in part due to its dual acid and base © 2012 American Chemical Society

Received: March 16, 2012 Revised: May 24, 2012 Published: July 5, 2012 16144

dx.doi.org/10.1021/jp302532n | J. Phys. Chem. C 2012, 116, 16144−16153

The Journal of Physical Chemistry C

Article

The total energy of the system was converged to less than 5.0 × 10−6 eV, the residual force less than 0.01 eV/Å, the displacement of atoms less than 5.0 × 10−4 Å, and the residual bulk stress less than 0.02 GPa. The hydrostatic pressures of 0− 300 GPa have been exerted on the unit cell to study the pressure effect on the geometrical and electronic structures of ATAN.

Although the highest pressures that can be achieved inside a diamond anvil cell and in a dynamic shockwave are about 320 GPa and 100 GPa, respectively,34 computational methods have competitive advantages since these allow a wide range of pressures to be explored relatively easily and have the potential to provide detailed information under extreme conditions, which is often difficult to obtain from experiment for practical reasons. There are sufficient computational investigations on the crystal structures and properties of materials including explosives such as RDX, 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX), and hexanitrohexaazaisowurtzitane (CL-20) under a wide range of pressures.47−58 In our previous study on 2-diazo-4,6-dinitrophenol (DDNP), we found that the DDNP molecule exists in the quinoid form when the pressure is below 10 GPa, while it has the cyclic azoxy form when the pressure is above 10 GPa.59 However, the investigations on energetic ionic salt crystal under high pressures are few, especially for 3-azido1,2,4-triazolium nitrate (ATAN)30 its high-pressure study has not been reported. Hence, first-principle periodic calculations have been performed using density functional theory (DFT) to study the effect of high pressure on the crystal structure of ATAN in this study.

3. RESULTS AND DISCUSSION As is known that results obtained from GGA and LDA are somewhat contradictory,65−69 therefore, to benchmark the performances of LDA and GGA, these two functionals have been applied to the bulk ATAN as a test. The LDA in the CAPZ scheme and GGA in the (Perdew−Burke−Ernzerhof) PBE70 and Perdew−Wang-91(PW91)71 schemes were selected to fully relax the ATAN at ambient pressure without any constraint. Table 1 presents the lattice constants obtained from these three methods, along with the experimental data for ATAN. The relative errors of the calculated values to the experimental ones show that the LDA/CA-PZ results agree better with the experimental ones than those of GGA; for example, the mean relative errors of lattice constants for the three methods are −2.424%, 9.257%, and 10.347%, respectively. Obviously, the deviation of LDA results is the smallest. This is also the case for bond lengths and angles. The calculated lattice constants are in good agreement with the experimental values, which indicates LDA can successfully predict the structure and properties of ATAN crystal. Thus, the LDA/ CA-PZ method has been employed in this study. 3.1. Crystal Structures and Energies. The relaxed lattice constants (a, b, c) of ATAN crystal under different hydrostatic pressures are depicted in Figure 2a. Obviously, a, b, and c decrease steadily with the pressure increasing. This is not consistent with our previous studies58 on organic compounds, in which there are abrupt changes in the descending trend of a, b, and c. This also suggests that the structures of salts are much stabler than those of organic compounds at high pressure. To compare the degree of lattice constants being compressed, the variation in the compressibility rates of a, b, and c with the pressure are calculated and showed in Figure 2b. As is evident, the largest compression of the unit cell takes place in the region of low pressures, and the lattice parameters decrease little with the increasing pressure. This is because the external pressure will induce structural changes in crystal materials by changing the binding forces that hold together molecules and atoms. When the pressure is low, the distance between molecules is far; correspondingly, the intermolecular repulsion is not large, and the crystal is comparatively more compressible as compared with chemical bonds. While under higher pressure, the intermolecular repulsion is larger, therefore, the crystal is more difficult to be compressed. Hence, the first structural response to an applied pressure in the crystal is the reduction of structural voids. As can also be seen, the compressibilities along three directions are not tantamount, which indicates that the compressibility of ATAN crystal is anisotropic. When the pressure is lower than 20 GPa, the compressibility in the bdirection is significantly greater than those in the a- and cdirections, and they follow the sequence of b > a > c. For example, from 0 GPa to 10 GPa, the unit cell is compressed by 6.20%, 11.95%, and 4.39% along the directions of a, b, and c, respectively, which shows that the structure is much stiffer in the c-direction than in the b- and a-directions. However, the

2. COMPUTATIONAL METHODS First-principle calculations were performed using DFT in combination with the Vanderbilt-type ultrasoft pseudopotential59 incorporated in the CASTEP code.60 The electronic wave functions were obtained within the Pulay density-mixing scheme61 and the structures were optimized by the BFGS method.62 The local density approximation (LDA) with the Ceperley−Alder exchange-correlation potential parametrized by Perdew and Zunger (CA-PZ)63,64 were used to perform the test calculations on crystalline ATAN. The cutoff energy of plane waves was set to 400.0 eV and Brillouin zone sampling was performed by using the Monkhost−Pack scheme with a kpoint grid of 3 × 2 × 2, which were determined to ensure the convergence of total energies. The initial structure adopted the experimental crystalline structure in which ATAN crystallizes in the orthorhombic space group Pnma with a = 8.3615 Å, b = 5.9374 Å, and c = 12.9129 Å, and contains 60 atoms per unit cell as shown in Figure 1.

Figure 1. Experimental unit cells and atomic numbering of ATAN.30 16145



Article

Table 1. Comparison of the Lattice Constants Obtained with LDA/CA-PZ, GGA/PBE, GGA/PW91, and the Experimental Data for ATAN at Ambient Pressure CA-PZ PBE PW91 exptl

a

reaa

b

reb

c

rec

meb

8.262 8.536 8.552 8.362

(−1.186) (2.086) (2.280)

5.690 6.992 7.176 5.937

(−4.166) (17.769) (20.867)

12.665 13.935 13.932 12.913

(−1.920) (7.916) (7.895)

−2.424 9.257 10.347

a

re means the relative error of the calculated values to the experimental ones, given in the parentheses in percent. bme means the average error of the absolute relative ones.

Figure 2. Optimized lattice constants (a, b, and c) and their compression rates as functions of pressure.

compressibilities change irregularly and significantly, that in adirection increases sharply to 1.15%, that in c-direction increases slightly to 0.68%, while that in b-direction decreases abruptly to 0.12%. Additionally, the crystal symmetry maintains the same orthorhombic space group Pnma under all hydrostatic compressions as the one determined experimentally. The unit cell volume (V), density (ρ), and total energy (Etot) of ATAN crystal under different hydrostatic pressures are depicted in Figure 4. Since a, b, and c decrease gradually with the pressure increasing, so does V, and correspondingly, the crystal density (ρ) increases as the pressure increases. Comparatively, the change in V and ρ is more pronounced in the low-pressure range. Etot of the unit cell rises linearly with the increasing pressure, which indicates that the intermolecular interactions increase as the molecules approach each other. Different from the changes in a, b, c, V, and ρ, Etot rises linearly with the increasing pressure. The good linear relationship can be shown from the correlation coefficient (R) 0.9997. This has not been found in our studies on organic compounds.58 3.2. Molecular Structure. The pressure causes the changes in not only the unit cell but also the molecular geometry. Some important geometrical parameters related to azide−tetrazole ring−chain isomerism and hydrogen bonding, including bond lengths, and bond angles, and some important interatomic distance at various pressures are presented in Figure 5. Figure 5a gives the variations of the bond lengths in 3-azido-1,2,4triazolium cation with the pressure. As the H atoms attached to the triazolium ring are easy to form the hydrogen bonds with the O atoms of nitrate, Figure 5b provides the variations of interatomic distance O13···H10, O13···H11, and N8···H9. For N8···H9, N8 and H9 are not in the same cation, and H9 is the H atom attached to the adjacent cation. The azide−tetrazole ring−chain isomerism for azide compounds has been the

compression order is b > c > a in the range of 30−190 GPa, and the higher the pressure, the closer the compression rates in the three directions. For instance, the compression along the directions of a, b, and c from 20 to 30 GPa are 1.95%, 3.32%, and 2.13%, respectively, while, from 170 to 180 GPa, they are 0.44%, 0.68%, and 0.45%, respectively. This can be interpreted from the perspective view of crystalline ATAN along three directions in Figure 3. All the atoms display layered structure in

Figure 3. Perspective views of ATAN crystal along various directions.

ATAN crystal. The layers are vertical to the b-axis, and the intermolecular distance along b-axis is the farthest; consequently, the compressibility along the b-direction is the largest. The distance between the layers decreases with the pressure increasing, so the unit cell is more and more difficult to be compressed in the b-direction. At 200 GPa, the 16146



Article

Figure 4. Unit cell volume, density, and total energy as a function of pressure.

Figure 5. Variation of the interatomic distances and bond angles with pressure.

subject of many studies, but previous studies mainly performed in solutions, the gas phase, or in the melt.72−76 The transformation in the crystal induced by the high pressure has not been reported. So the aim of this study focuses on azide−tetrazole ring−chain isomerism. Figure 5c,d presents the

variation of interatomic distance N2···N8 and bond angles N6− N7−N8, C3−N6−N7, and N2−C3−N6, respectively. The perspective views of one layer of ATAN unit cell at different pressures are displayed more intuitionistically and visually in Figure 6. 16147



Article

Figure 6. Perspective views of one layer of ATAN unit cell at different pressures.

tetrazole is not completely transformed from azide, and the distance of N2···N8 (2.233 Å) also validates this conclusion. When the pressure reaches 200 GPa, there are remarkable changes in molecular geometry, though the changes in unit cell lattice constants, unit cell volume, density, and total energy at this pressure are little, but compression rate as a function of pressure reflects this point (seen in Figure 2). Concretely, the covalent bonds elongate or shorten evidently; especially for N1−H9, it elongates sharply from 1.078 at 190 GPa to 1.495. Simultaneously, N8···H9 shortens suddenly to 1.054 Å. Both indicate that the H9 atom has transferred from N1 to N8 and a new covalent bond forms, that is, transfer of hydrogen is induced by high pressure. N6−N7−N8 decreases to 116.03°, much closer to 108°, but unfortunately, N2−C3−N6 deviates more from 108°; thus, tetrazole is not completely transformed from azide. When the pressure increases further until 300 GPa, azide− tetrazole transformation has not completely been realized owing to being affected by this new covalent bond. The molecular structure keeps almost unchanged, that is to say, a kind of new structure may be built to resist the higher external pressure. It is worth noting that, within the whole pressure passage, all atoms in one layer are still in the plane and that the triazole ring has not distorted. 3.3. Electronic Structure. 3.3.1. Atom and Bond Populations. To better explain the effect of pressure on the electron density redistribution in the cyclization and hydrogen

When the hydrostatic pressure increases from 0 to 20 GPa, the bond lengths in 1,2,4-triazolium shorten slightly, while interatomic distance (O13···H10, O13···H11, N8···H9, and N2···N8) shorten sharply, which implies that the applied compression mostly squeezes out the intermolecular space and causes only a little change in intramolecular geometry. As very low pressure is applied, the distances of O13···H10 and O13···H11 are nearly shorter than 2.0 Å, which implies that hydrogen bonding generates in N4−H11···O13 and C5− H10···O13. The bond angles C3−N6−N7 decreases from 114.44° to 106.97°, close to 108°, the internal angle of pentagon. N2−C3−N6 decreases slightly from 125.39° to 122.32°. It is worth while to note that the directions of the bond angle N6−N7−N8 at 0 and 10 GPa are opposite to those at other pressures and that N6−N7−N8 at 20 GPa is the closest to 180° (seen in Figure 6). From 20 to 190 GPa, bonds N1−N2, C3−N4, N4−C5, N1− C5, C3−N6, N6−N7 and so on shorten slightly, while N2−C3 and N7−N8 lengthen abnormally due to the further bending of N6−N7−N8. The change in the covalent bond lengths is little, which indicates that the repulsion between the two bonding atoms is enough to resist the external pressure. Four interatomic distances shorten gradually and obviously. In this pressure region, the bond angles C3−N6−N7 and N2−C3−N6 increase slightly with the pressure increasing; N6−N7−N8 decreases gradually and evidently from about 180° at 20 GPa to 131.91°, which is markedly larger than 108°. This means 16148



Article

Figure 7. Atomic charges and bond populations in ATAN at different pressures.

Figure 8. Self-consistent band structures of bulk ATAN under different pressures. The Fermi energy is shown as a dashed horizontal line.

transfer, the variations of atom charges and bond populations with the increasing pressure are investigated. As is well-known

that the absolute magnitude of the atomic charges yielded by population analysis have little physical meaning, they display a 16149



Article

high degree of sensitivity to the atomic basis set with which they were calculated.77 However, consideration of their relative values can yield useful information.78−80 Figure 7a,b depicts the variation trends of the atomic charges with pressure for crystalline ATAN. When the pressure is below 30 GPa, both the positive charges on C3, H9, H10, and H11 and the negative charges on N1, N4, N6, and O13 decrease gradually and obviously, while the positive charges on C5 and N7 as well as the negative ones on N2 and N8 increase with the increase in pressure. These suggest that high pressure can promote the increase in the delocalization degree of electrons. From 30 to 200 GPa, the atom charges change slightly and tend to be more delocalized. The biggest changes occur on N2 and N8. The negative charge on N8 increases substantially and that on N2 decreases significantly about 0.2e, while the change on N7 is only 0.04e. This means that the charges transfer from N2 to N8 and that the azide chain is tending to tetrazole ring. When the pressure reaches 200 GPa from 190 GPa, N8 obtains more charges (about 0.13e) from N2, but unfortunately, N8 with more negative charges bonds with the H atom attached to the adjacent cation; thus, the tetrazole ring cannot form. Figure 7c,d shows the bond populations of several bonds with pressure for crystalline ATAN. Usually, the higher the bond population, the more covalent the bond.79 Under the pressure from 30 to 190 GPa, the bending of the angle N6− N7−N8 causes a slight decrease in the bond population of N7− N8, while that of N6−N7 are kept unchanged. As for those of N1−H9 and N8−H9, they increase a little with the increasing pressure. When the pressure is boosted to 200 GPa, the bond population of N1−H9 reduces from 0.77 to 0.19 and that of N8−H9 rises from 0.10 to 0.78, which indicates that H9 transfers from N1 to N8. Moreover, N7−N8 decreases greatly because N8 bonds with H9 and thus weakens the intensity of N7−N8. 3.3.2. Band Structure and Density of States. On the basis of the equilibrium crystal structures obtained at different pressures, the self-consistent band structures along different symmetry directions of the Brillouin zone have been calculated and depicted in Figure 8. Only the bands between −2.0 and 4.0 eV are presented for the sake of brevity. It can be seen that the energy bands including valence and conduction bands are very flat when pressure is very low. As the pressure increases, they fluctuate more and more obviously and shift to lower energy region; thus, the widths of the energy bands broaden compared with those under lower pressures, and the energy gap (ΔEg) between the highest occupied crystal orbital (HOCO) and the lowest unoccupied crystal orbital (LUCO) decrease gradually. On account of the transformation in configuration of ATAN at 200 GPa, significant changes in the electronic properties are observed. The difference in the band structures between 190 and 200 GPa is more evident than those at other pressures. The calculated band gaps of ATAN as a function of pressure is shown in Figure 9. In the range of 0−190 GPa, ΔEg decreases gradually with the pressure increasing, but the average decrease in different pressure ranges is different, for example, ΔEg decreases by 14.0% from 0 to 10 GPa, while only 3.8% from 70 to 80 GPa. This discrepancy in the ΔEg reduction may be caused by the different compressibility degree of the crystal in different pressure region, which implies that the electronic structure will change subtly even though no obvious molecular geometry variation occurs. Since ΔEg is related to the sensitivity

Figure 9. Band gap of solid ATAN as a function of pressure.

of the material, according to principle of the easiest transition (PET) of electrons,81 it can be concluded that the sensitivity increases as the pressure increases. When the pressure turns into 200 GPa, ΔEg augments dramatically to 0.645 eV due to the structural transformation of ATAN molecule. The reason is that the incomplete azide−tetrazole transformation at this pressure results in a conjunction system and increases the delocalization in the system, correspondingly, the lowest valence band shifts to lower energy, and therefore, the band gap gets larger. From 200 to 300 GPa, ΔEg decreases slightly because the molecular geometry and lattice constants scarcely change in the high pressure region although the external pressure increases greatly; thus the increasing internal stress decreases the delocalization, and the lowest valence band shifts to higher energy. An analysis of densities of states (DOS) is helpful to understand the changes in electronic structure caused by external pressure. Some characteristics such as the width of the valence band, the energy gap, and the number and intensity of the main peaks can be used to qualitatively interpret experimental spectroscopic data. Furthermore, DOS analysis may help us to better understand the changes in electronic structure caused by external pressure. Figure 10 depicts the calculated DOS for bulk ATAN at different pressures. As can be easily seen, the higher the pressure, the lower and wider the peaks are. When the pressure is low, the curves of DOS are characterized by obvious peaks, but with increasing pressure, the peaks widen gradually, which means that the band splitting and band dispersion increase accompanied by a broadening of DOS. Accordingly, electronic nonlocality in bulk ATAN gradually increases. When the pressure is 300 GPa, the DOS becomes smooth, and DOS in each energy region is approximately equal. This implies that electrons have become delocalized and can move freely in the valence and conduction bands, thus the ATAN crystal becomes a metal at high pressure,82−85 but during detonation of the conventional explosives, the generation of this state is physically impossible. Moreover, the conduction bands have a tendency of shifting to the lower energy, consequently leading to a reduction in ΔEg and showing that crystal compression greatly increases the probability of electronic excitations, which is in good agreement with the conclusion drawn from the analysis of band gap. Because the DOS curves contain some form of broadening effect, they are finite at the Fermi energy level. Within the lower pressure range, the sharp peaks of valence and conduction band 16150



Article

Figure 10. Calculated total DOS for bulk ATAN at different pressures: s, p, and total states are shown as dotted, dashed, and solid curves, respectively.

near the Fermi level are predominantly composed from the p states, which indicates that the p states play a very important role in chemical reaction of ATAN. With the increase in pressure, it is superimposed by the p and s states.

unchanged, azide−tetrazole transformation has not completely been realized owing to being affected by this new covalent bond. High pressure can promote the increase in the delocalization degree of electrons. From 30 to 200 GPa, The negative charge on N8 increases substantially and that on N2 decreases significantly. This means that the charges transfer from N2 to N8 and azide chain is tending to tetrazole ring. When the pressure reaches 200 GPa from 190 GPa, N8 obtains more charges from N2, but N8 with more negative charges bonds with the H atom attached to the adjacent cation; thus, the tetrazole ring cannot form completely. When the pressure is boosted to 200 GPa, the bond population of N1−H9 reduces from 0.77 to 0.19 and that of N8−H9 rises from 0.10 to 0.78, which indicates that H9 transfers from N1 to N8. Moreover, N7−N8 decreases greatly because N8 bonds with H9 and thus weaken the intensity of N7−N8. Similarly, as the pressure increases, the band gap gradually decreases, but it becomes anomalously large at 200 GPa due to the structural transformation, and the analysis to density of states indicates that the electronic delocalization increases under the influence of pressure. This shows that an exerted pressure may increase the impact sensitivity of the energetic ionic salt. The azide−tetrazole ring−chain isomerism for azide compounds in the crystal induced by the high pressure has not been reported. We think this work may provide useful information in understanding the high-pressure behavior of ATAN and may offer enhanced opportunities to discover some new structures that are generally inaccessible at normal conditions.

4. CONCLUSIONS In this study, DFT calculations have been performed to investigate the geometrical and electronic structures of the crystalline ATAN in the range of 0−300 GPa. The LDA/CAPZ functional, which can successfully reproduce the experimental crystal structure of ATAN, was adopted. The lattice constants decrease gradually with the pressure increasing, but the variation in the compressibility rates of a, b, and c change irregularly and significantly at 200 GPa. The Etot of the unit cell rises linearly with the increasing pressure and the linear correlation coefficient (R) 0.9997. When the hydrostatic pressure increases from 0 to 20 GPa, the applied compression mostly squeezes out the intermolecular space and causes only a little change in intramolecular geometry. From 20 to 190 GPa, all bonds shorten slightly except that N2−C3 and N7−N8 lengthen abnormally due to the further bending of the azide group. N6−N7−N8 decreases gradually and evidently from about 180° at 20 GPa to 131.91°. This means tetrazole is transforming from azide, but when the pressure reaches 200 GPa, there are remarkable changes in molecular geometry. N6−N7−N8 decreases to 116.03°, and N1−H9 elongates sharply from 1.078 at 190 GPa to 1.495. Simultaneously, N8···H9 shortens suddenly to 1.054 Å. Both indicate that the H9 atom has transferred from N1 to N8 and a new covalent bond forms. When the pressure increases further until 300 GPa, the molecular structure keeps almost 16151



■

Article

(27) Huang, H. F.; Zhou, Z. M.; Liang, L. X.; Song, J. H.; Wang, K.; Cao, D.; Bian, C. M.; Sun, W. W.; Xue, M. Z. Anorg. Allg. Chem. 2012, 638, 392−400. (28) Huang, Y. G.; Zhang, Y. Q.; Shreeve, J. M. Chem.Eur. J. 2011, 17, 1538−1546. (29) Chavez, D. E.; Gilardi, R. D. J. Energy Mater. 2009, 27, 110−117. (30) Xue, H.; Gao, Y.; Twamley, B.; Shreeve, J. M. Chem. Mater. 2005, 17, 191−198. (31) Manaa, M. R.; Fried, L. E.; Reed, E. J. J. Comput.-Aided Mater. Des. 2003, 10, 75−97. (32) Peiris, S. M.; Wong, C. P.; Zerilli, F. J. J. Chem. Phys. 2004, 120, 8060−8066. (33) Fabbiani, F. P. A.; Pulham, C. R. Chem. Soc. Rev. 2006, 35, 932− 942. (34) Boldyreva, E.; Dera, P. High-Pressure Crystallography: From Fundamental Phenomena to Technological Applications; Springer Science Business Media B.V.: Dordrecht, The Netherlands, 2010; pp 447−457. (35) Patterson, J. E.; Dreger, Z. A.; Gupta, Y. M. J. Phys. Chem. B 2007, 111, 10897−10904. (36) Lipinska-Kalita, K. E.; Pravica, M. G.; Nicol, M. J. Phys. Chem. B 2005, 109, 19223−19227. (37) Pravica, M.; Shen, Y. R.; Quine, Z.; Romano, E.; Hartnett, D. J. Phys. Chem. B 2007, 111, 4103−4108. (38) Dreger, Z. A.; Gupta, Y. M. J. Phys. Chem. B 2007, 111, 3893− 3903. (39) Ciezak, J. A.; Jenkins, T. A.; Liu, Z. X.; Hemley, R. J. J. Phys. Chem. A 2007, 111, 59−63. (40) Millar, D. I. A.; Marshall, W. G.; Oswald, I. D. H.; Pulham, C. R. Cryst. Rev. 2010, 16, 115−132. (41) Dong, Z. H.; Beilby, N. G.; Huang, Y. N.; Song, Y. J. Chem. Phys. 2008, 128, 074501−9. (42) Ricardo, I. C.; Leonardo, C. P. L.; Samuel, P. H. R. J. Mol. Struct. 2010, 970, 51−58. (43) Sorescu, D. C.; Rice, B. M.; Thompson, D. L. J. Phys. Chem. B 1999, 103, 6783−6790. (44) Byrd, E. F. C.; Rice, B. M. J. Phys. Chem. C 2007, 111, 2787− 2796. (45) Sorescu, D. C.; Rice, B. M. J. Phys. Chem. C 2010, 114, 6734− 6748. (46) Zerilli, F. J.; Kuklja, M. M. J. Phys. Chem. A 2006, 110, 5173− 5179. (47) Zerilli, F. J.; Hooper, J. P.; Kuklja, M. M. J. Chem. Phys. 2007, 126, 114701−10. (48) Zerilli, F. J.; Kuklja, M. M. J. Phys. Chem. A 2007, 111, 1721− 1725. (49) Zhu, W. H.; Zhang, X. W.; Wei, T.; Xiao, H. M. Theor. Chem. Acc. 2009, 124, 179−186. (50) Margetis, D.; Kaxiras, E.; Elstner, M.; Frauenheim, T.; Manaa, M. R. J. Chem. Phys. 2002, 117, 788−799. (51) Liu, H.; Zhao, J. J.; Wei, D. Q.; Gong, Z. Z. J. Chem. Phys. 2006, 124, 124501−10. (52) Zhao, J. J.; Liu, H. Comput. Mater. Sci. 2008, 42, 698−703. (53) Qiu, L.; Zhu, W. H.; Xiao, J. J.; Xiao, H. M. J. Phys. Chem. B 2008, 112, 3882−3893. (54) Xu, X. J.; Zhu, W. H.; Xiao, H. M. J. Phys. Chem. B 2007, 111, 2090−2097. (55) Mujica, A.; Rubio, A.; Muñoz, A.; Needs, R. J. Rev. Mod. Phys. 2003, 75, 863−912. (56) Ma, Y. M.; Oganov, A. R.; Li, Z. W.; Xie, Y.; Kotakoski, J. Phys. Rev. Lett. 2009, 102, 065501−. (57) Millar, D. I. A.; Oswald, I. D. H.; Francis, D. J.; Marshall, W. G.; Pulham, C. R.; Cumming, A. S. Chem. Commun. 2009, 562−564. (58) Liu, Y.; Gong, X. D.; Wang, L. J.; Wang, G. X. J. Phys. Chem. C 2011, 115, 11738−11748. (59) Vanderbilt, D. Phys. Rev. B 1990, 41, 7892−7895. (60) Clark, S. J.; Segall, M. D.; Pickard, C. J.; Hasnip, P. J.; Probert, M. J.; Refson, K.; Payne, M. C. Z. Kristallogr. 2005, 220, 567−570. (61) Kresse, G.; Furthmüller, J. Phys. Rev. B 1996, 54, 11169−11186. (62) Fischer, T. H.; Almlof, J. J. Phys. Chem. 1992, 96, 9768−9774.

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected] (L.W.); gongxd325@mail. njust.edu.cn (X.G.). Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS We gratefully thank the Major Project of Water Pollution Control and Management Technology of China (No. 2012ZX07101-003-001), the National Natural Science Foundation of China (Grant No.11076017), the Research Fund for the Doctoral Program of Higher Education of China (No. 20103219120014), the NUST Research Funding (No. 2011YBXM68) for the support of this work.

■

REFERENCES

(1) Korkin, A. A.; Bartlett, R. J. J. Am. Chem. Soc. 1996, 118, 12244− 12245. (2) Leininger, M. L.; Sherrill, C. D.; Schaefer, H. J. Phys. Chem. 1995, 99, 2324−2328. (3) Strout, D. L. J. Phys. Chem. A 2004, 108, 10911−10916. (4) Fried, L. E.; Manaa, M. R.; Pagoria, P. F.; Simpson, R. L. Annu. Rev. Mater. Res. 2001, 31, 291−323. (5) Gao, H. X.; Shreeve, J. M. Chem. Rev. 2011, 111, 7377−7436. (6) Singh, R. P.; Verma, R. D.; Meshri, D. T.; Shreeve, J. M. Angew. Chem., Int. Ed. 2006, 45, 3584−3601. (7) Gutowski, K. E.; Holbrey, J. D.; Rogers, R. D.; Dixon, D. A. J. Phys. Chem. B 2005, 109, 23196−23208. (8) Wang, R. H.; Guo, Y.; Sa, R. J.; Shreeve, J. M. Chem.Eur. J. 2010, 16, 8522−8529. (9) Singh, R. P.; Gao, H. X.; Meshri, D. T.; Shreeve, J. M. Struct. Bonding 2007, 125, 35−83. (10) Hiskey, M. A.; Chavez, D. E.; Naud, D. L.; Son, S. F.; Berghout, H. L.; Bolme, C. A. Proc. Int. Pyrotech. Semin. 2000, 27, 3−14. (11) Joo, Y. H.; Shreeve, J. M. Angew. Chem., Int. Ed. 2009, 48, 564− 567. (12) Xue, H.; Gao, Y.; Twamley, B.; Shreeve, J. M. Inorg. Chem. 2005, 44, 5068−5072. (13) Zhang, Y. Q.; Guo, Y.; Joo, Y. H.; Parrish, D. A.; Shreeve, J. M. Chem.Eur. J. 2010, 16, 10778−10784. (14) Zhang, Y. Q.; Parrish, D. A.; Shreeve, J. M. Chem.Eur. J. 2012, 18, 987−994. (15) Abe, T.; Tao, G. H.; Joo, Y. H.; Winter, R. W.; Gard, G. L.; Shreeve, J. M. Chem.Eur. J. 2009, 15, 9897−9904. (16) Klapötke, T. M.; Sabate, C. M. Z. Anorg. Allg. Chem. 2009, 635, 1812−1822. (17) Leonard, P. W.; Chavez, D. E.; Pagoria, P. F.; Parrish, D. L. Propellants, Explos., Pyrotech. 2011, 36, 233−239. (18) Wang, R. H.; Guo, Y.; Zeng, Z.; Twamley, B.; Shreeve, J. M. Chem.Eur. J. 2009, 15, 2625−2634. (19) Nag, S.; Bhowmik, S.; Gauniyal, H. M.; Batra, S. Eur. J. Org. Chem. 2010, 4705−4712. (20) Wang, R. H.; Xu, H. Y.; Guo, Y.; Sa, R.; Shreeve, J. M. J. Am. Chem. Soc. 2010, 132, 11904−11905. (21) Thottempudi, V.; Gao, H. X.; Shreeve, J. M. J. Am. Chem. Soc. 2011, 133, 6464−6471. (22) Xue, H.; Gao, H. X.; Twamley, B.; Shreeve, J. M. Chem. Mater. 2007, 19, 1731−1739. (23) Carlson, P. J.; Bose, S.; Armstrong, D. W.; Hawkins, T.; Gordon, M. S.; Petrich, J. W. J. Phys. Chem. B 2012, 116, 503−512. (24) Xue, H.; Shreeve, J. M. Adv. Mater. 2005, 17, 2142−2146. (25) Wang, K.; Parrish, D. A.; Shreeve, J. M. Chem.Eur. J. 2011, 17, 14485−14492. (26) Klapöke, T. M.; Krumm, B.; Martin, F. A.; Stierstorfer, J. Chem. Asian J. 2012, 7, 214−224. 16152



Article

(63) Ceperley, D. M.; Alder, B. J. Phys. Rev. Lett. 1980, 45, 566−569. (64) Perdew, J. P.; Zunger, A. Phys. Rev. B 1981, 23, 5048−5079. (65) Byrd, E. F. C.; Rice, B. M. J. Phys. Chem. C 2007, 111, 2787− 2796. (66) Zoroddu, A.; Bernardini, F.; Ruggerone, P.; Fiorentini, V. Phys. Rev. B 2001, 64, 045208−6. (67) Mehta, S.; Price, G. D.; Alfè, D. J. Chem. Phys. 2006, 125, 194507. (68) Cococcioni, M.; Corso, A. D.; Gironcoli, S. Phys. Rev. B 2003, 67, 094106−. (69) Liu, H.; Zhao, J. J.; Du, J. G.; Gong, Z. Z.; Ji, G. F.; Wei, D. Q. Phys. Lett. A 2007, 367, 383−388. (70) Perdew, J. P.; Burke, K.; Ernzerhof, M. Phys. Rev. Lett. 1996, 77, 3865−3868. (71) Perdew, J. P.; Wang, Y. Phys. Rev. B 1992, 45, 13244−13249. (72) Cubero, E.; Orozco, M.; Luque, F. J. J. Am. Chem. Soc. 1998, 120, 4723−4731. (73) Dabbagh, H. A.; Wowski, W. L. J. Org. Chem. 2000, 65, 7284− 7290. (74) Zheng, W. X.; Wong, N. B.; Liang, X. Q.; Long, X. P.; Tian, A. M. J. Phys. Chem. A 2004, 108, 840−847. (75) Hammerl, A.; Klapötke, T. M.; Rocha, R. Eur. J. Inorg. Chem. 2006, 2210−2228. (76) Kessenich, E.; Polborn, K.; Schulz, A. Inorg. Chem. 2001, 40, 1102−1109. (77) Davidson, E. R.; Chakravorty, S. Theor. Chim. Acta 1992, 83, 319−330. (78) Segall, M. D.; Pickard, C. J.; Shah, R.; Payne, M. C. Mol. Phys. 1996, 89, 571−577. (79) Segall, M. D.; Shah, R.; Pickard, C. J.; Payne, M. C. Phys. Rev. B 1996, 54, 16317−16320. (80) Winkler, B.; Pickard, C. J.; Segall, M. D.; Milman, V. Phys. Rev. B 2001, 63, 14103−9. (81) Xiao, H. M.; Li, Y. F. Sci. China, Ser. B: Chem. 1995, 38, 538− 545. (82) Wu, C. J.; Yang, L. H.; Fried, L. E.; Quenneville, J.; Martinez, T. J. Phys. Rev. B 2003, 67, 235101. (83) Yasuzuka, S.; Murata, K. Sci. Technol. Adv. Mater. 2009, 10, 024307−18. (84) Jiang, Y.; Wu, K. H.; Ma, J.; Wu, B.; Wang, E. G.; Ebert, P. Phys. Rev. B 2007, 76, 235434−. (85) Shakhvorostov, D.; Nistor, R. A.; Krusin-Elbaum, L.; Martyna, G. J.; Newns, D. M.; Elmegreen, B. G.; Liu, X. H.; Hughes, Z. E.; Paul, S.; Cabral, C.; Raoux, S.; Shrekenhamer, D. B.; Basov, D. N.; Song, Y.; Müser, M. H. Proc. Natl. Acad. Sci. U.S.A. 2009, 106, 10907−10911.

16153


First-Principle Studies on the Pressure-Induced Structural Changes in

Recommend Documents