Finite temperature string by -means clustering sampling with order parameters as collective variables for molecular crystals: application to polymorphic transformation between β-CL-20 and ε-CL-20.

Polymorphic transformation of molecular crystals is a fundamental phase transition process, and it is important practically in the chemical, material, biopharmaceutical, and energy storage industries. However, understanding of the transformation mechanism at the molecular level is poor due to the extreme simulating challenges in enhanced sampling and formulating order parameters (OPs) as the collective variables that can distinguish polymorphs with quite similar and complicated structures so as to describe the reaction coordinate. In this work, two kinds of OPs for CL-20 were constructed by the bond distances, bond orientations and relative orientations.

Experimental and theoretical investigation into the response to shock wave for booster explosives JO9C, JH14, JH6, and insensitive RDX.

In order to reduce the vulnerability, the responses to shock waves for booster explosives JO9C, JH14, JH6, and insensitive RDX were evaluated using shock wave partition loading test. To explain the experimental results, molecular dynamics simulation, intermolecular interaction and bond dissociation energy (BDE), and shock initiation pressures were evaluated using the B3LYP, MP2 (full), and M06-2X methods with the 6-311 +  + G(2df,2p) basis set. The order of the responsivity is JO9C > JH14 > JH6 > insensitive RDX.

External electric field reduces the explosive sensitivity: a theoretical investigation into the hydrogen transference kinetics of the NHNO∙∙∙HO complex.

Controlling the selectivity of detonation initiation reaction to reduce the explosive sensitivity has been a Holy Grail in the field of energetic materials. The effects of the external electric fields on the homolysis of the N-NO bond and initiation reaction dynamics of NHNO∙∙∙HO (i.e.

Hydration and swelling: a theoretical investigation on the cooperativity effect of H-bonding interactions between p-hydroxy hydroxymethyl calix[4]/[5]arene and HO by many-body interaction and density functional reactivity theory.

In order to explore the nature of the hydration and swelling of superabsorbent resin, a theoretical investigation into the cooperativity effect of the H-bonding interactions in the hydrates of four model compounds that can be regarded as the units of hydroquinone formaldehyde resin (HFR) (i.e., O-hydroxymethyl-1,4-dihydroxybenzene, methylene di-O-hydroxymethyl-1,4-dihydroxybenzene, p-hydroxy hydroxymethyl calix[4]arene and p-hydroxy hydroxymethyl calix[5]arene) was carried out by many-body interaction and density functional reactivity theory.

A dynamic and electrostatic potential prediction of the prototropic tautomerism between imidazole 3-oxide and 1-hydroxyimidazole in external electric field.

In order to obtain an optimum scheme for separating the proton-transfer tautomer, a dynamic investigation into the effect of the external electric field on the proton-transfer tautomeric conversion in imidazole 3-oxide and 1-hydroxyimidazole was carried out at the M06-2X/6-311++G** and CCSD(T)/6-311++G(2d,p) level, accompanied by the analysis of the surface electrostatic potentials. The results show that, for both the forward reaction "imidazole 3-oxide → N-hydroxyimidazole free radical → 1-hydroxyimidazole" and its reverse reaction processes, the fields parallel to the N→O or N-OH bond axis affect the barrier heights and rate constants considerably more than those parallel to the other orientations. As the field strength is increased along the orientation from the O to N atom, the chemical equilibrium moves toward the direction for the formation of 1-hydroxyimidazole, while the amount of imidazole 3-oxide is increased with the increased field strength along the opposite orientation.

Theoretical investigation into the cooperativity effect between the intermolecular π∙π and H-bonding interactions in the curcumin∙cytosine∙HO system.

In order to reveal the mechanism of drug action and design of DNA/RNA-targeted drugs containing aromatic rings, the cooperativity effects between the intermolecular π∙∙∙π and H-bonding interactions in curcumin(drug)∙∙∙cytosine(DNA/RNA base)∙∙∙HO were investigated by the B3LYP-D3 and MP2(full) methods with the 6-311++G(2d,p) basis set. The π∙∙∙π interaction plays an important role in stabilizing the linear ternary complexes with the cooperativity effects, and the cyclic structures suffer the anticooperativity effects. The cooperativity or anticooperativity effects are notable, which could lead to a possible significant change in drug activity.

A theoretical prediction of the relationships between the impact sensitivity and electrostatic potential in strained cyclic explosive and application to H-bonded complex of nitrocyclohydrocarbon.

Seven models that related the features of molecular surface electrostatic potentials (ESPs) above the bond midpoints and rings, statistical parameters of ESPs to the experimental impact sensitivities h 50 of eight strained cyclic explosives with the C-NO2 bonds were theoretically predicted at the DFT-B3LYP/6-311++G** level. One of the models was used to investigate the changes of h 50 for the nitrocyclohydrocarbon frameworks in the H-bonded complexes of HF with nitrocyclopropane, nitrocyclobutane, nitrocyclopentane, and nitrocyclohexane. The results show that the correlation coefficients of the obtained models are small.

A dynamics prediction of nitromethane → methyl nitrite isomerization in external electric field.

As a follow-up to our investigation into the effect of external electric field on the chemical bond strength, the effects of external electric field on the CH3NO2 → CH3ONO isomerization dynamics were investigated using the MP2/6-311++G(2d,p) and CCSD/6-311++G(2d,p) methods. The rate constants in the absence and presence of various field strengths were calculated. The results show that, when the field strength is larger than +0.

A theoretical prediction of the possible trigger linkage of CH3NO2 and NH2NO2 in an external electric field.

The effects of an external electric field on the C/N-NO2 bond with C/N-H and N-O bonds in CH3NO2 or NH2NO2 were compared using the DFT-B3LYP and MP2 methods with the 6-311++G(2d,p) and aug-cc-pVTZ basis sets. The results show that such fields have a minor effect on the C-N or C-H bond but a major effect on the N-O bond in CH3NO2, while in NH2NO2 electric fields affect the N-N bond greatly but the N-O or N-H bond only slightly. Thus, in CH3NO2, oxygen transfer or unimolecular isomerization to methyl nitrite might precede breaking of the C-N bond in the initial stages of decomposition, and the N-O bond could be the trigger bond in electric fields.

A B3LYP and MP2(full) theoretical investigation into the cooperativity effect between dihydrogen-bonding and H-M∙∙∙π (M = Li, Na, K) interactions among HF, MH with the π-electron donor C2H2, C2H4 or C6H6.

The DFT-B3LYP/6-311++G(3df,2p) and MP2(full)/6-311++G(3df,2p) calculations were carried out on the binary complex formed by HM (M = Li, Na, K) and HF or the π-electron donor (C2H2, C2H4, C6H6), as well as the ternary system FH∙∙∙HM∙∙∙C2H2/C2H4/C6H6. The cooperativity effect between the dihydrogen-bonding and H-M∙∙∙π interactions was investigated. The result shows that the equilibrium distances R(H∙∙∙H) and R(M∙∙∙π) in the ternary complex decrease and both the H∙∙∙H and H-M∙∙∙π interactions are strengthened when compared to the corresponding binary complex.

A comparative theoretical investigation into the strength of the trigger-bond in the Na⁺, Mg²⁺ and HF complexes involving the nitro group of R-NO₂ (R = -CH₃, -NH₂ and -OCH₃) or the C = C bond of (E)-O₂N-CH = CH-NO₂.

A comparative theoretical investigation into the change in strength of the trigger-bond upon formation of the Na(+), Mg(2+) and HF complexes involving the nitro group of RNO₂ (R = -CH₃, -NH₂, -OCH₃) or the C = C bond of (E)-O₂N-CH = CH-NO₂ was carried out using the B3LYP and MP2(full) methods with the 6-311++G**, 6-311++G(2df,2p) and aug-cc-pVTZ basis sets. Except for the Mg(2+)⋯π system with (E)-O2N-CH = CH-NO₂ (i.e.

3-(4,6-Dichloro-1,3,5-triazin-2-yl)-2,2-dimethyl-1,3-oxazolidine.

In the title compound, C(8)H(10)Cl(2)N(4)O, the dichloro-substituted triazine ring and the quasi-plane of the five-membered dimethyl-substituted oxazolidine unit, in which the O atom lies 0.228 (1) Å out of the least-squares plane, are close to being coplanar [dihedral angle = 4.99 (10)°].

2,2'-{[4,6-Bis(octyl-amino)-1,3,5-triazin-2-yl]aza-nedi-yl}diethanol.

In the title compound, C(23)H(46)N(6)O(2), the two hy-droxy groups are located on opposite sides of the triazine ring. One of the hy-droxy groups links with the triazine N atom via an intra-molecular O-H⋯N hydrogen bond. Inter-molecular O-H⋯N and N-H⋯O hydrogen bonding is observed in the crystal structure.

A B3LYP and MP2(full) theoretical investigation into explosive sensitivity upon the formation of the molecule-cation interaction between the nitro group of 3,4-dinitropyrazole and H+, Li+, Na+, Be2+ or Mg2+.

The explosive sensitivity upon the formation of molecule-cation interaction between the nitro group of 3,4-dinitropyrazole (DNP) and H(+), Li(+), Na(+), Be(2+) or Mg(2+) has been investigated using the B3LYP and MP2(full) methods with the 6-311++G** and 6-311++G(2df,2p) basis sets. The bond dissociation energy (BDE) of the C3-N7 trigger bond has also been discussed for the DNP monomer and the corresponding complex. The interaction between the oxygen atom of nitro group and H(+) in DNP…H(+) is partly covalent in nature.

3-Eth-oxy-2-hy-droxy-benzaldehyde 2,4-di-nitro-phenylhydrazone N,N-di-methyl-formamide monosolvate.

The Schiff base of the title compound, C(15)H(14)N(4)O(6)·C(3)H(7)NO, was obtained from the condensation reaction of 3-eth-oxy-2-hy-droxy-benzaldehyde and 2,4-dinitro-phenyl-hydrazine. The dihedral angle between the benzene rings is 3.05 (10)° and intra-molecular N-H⋯O and O-H⋯O hydrogen bonds generate S(6) and S(5) ring motifs, respectively.

2-Hydroxy-3-methoxybenzaldehyde 2,4-dinitrophenylhydrazone pyridine monosolvate.

The Schiff base molecule of the title compound, C(14)H(12)N(4)O(6)·C(5)H(5)N, was obtained from the condensation reaction of 2-hy-droxy-3-meth-oxy-benzaldehyde and 2,4-dinitro-phenyl-hydrazine. The C=N bond of the Schiff base has a trans arrangement and the dihedral angle between the two benzene rings is 3.49 (10)°.

A B3LYP and MP2 theoretical investigation into host-guest interaction between calix[4]arene and Li(+) or Na (+).

The DFT-B3LYP and MP2 methods with 6-311G** and 6-311++G** basis sets have been applied to study the complexation energies of the host-guest complexes between the cone calix[4]arene and Li(+) or Na(+) on the B3LYP optimized geometries. A comparison of the complexation energies obtained from the MP2(full) with those from MP2(fc) method is also carried out. The result shows that it is essential to introduce the diffuse basis set into the geometry optimizations and complexation energy calculations of the alkali-metal cation-pi interaction complexes of calix[4]arene, and the D (e) values show a maximum of 21.

A theoretical study on unusual intermolecular T-shaped X-H...pi interactions between the singlet state HB=BH and HF, HCl, HCN or H2C2.

The unusual T-shaped X-H...

3,6-Dibromo-9-(4-tert-butyl-benz-yl)-9H-carbazole.

In the title compound, C(23)H(21)Br(2)N, which was synthesized by the N-alkyl-ation of 1-tert-butyl-4-(chloro-meth-yl)benzene with 3,6-dibromo-9H-carbazole, the asymmetric unit contains two unique mol-ecules. Each carbazole ring system is essentially planar, with mean deviations of 0.0077 and 0.