Azo-Bridged Triazole Macrocycles: Computational Design, Energy Content, Performance, and Stability Assessment.

Oxadiazole and triazole are extensively investigated heterocyclic scaffolds in the development of energetic materials. New energetic molecules were designed by replacing 1,2,5-oxadiazole with 2H-1,2,3-triazole in the reported conjugated macrocyclic systems to assess the influence on the energetic properties and stability. In addition, nitro groups were introduced in triazole units (N-functionalization) to improve the energetic performance. Energetic properties, including heat of formation, oxygen balance, density, detonation pressure and velocity, and impact sensitivity, were estimated for these triazole-based macrocycles. The replacement of 1,2,5-oxadiazole with 2H-1,2,3-triazole and 2-nitro-1,2,3-triazole significantly enhances the energy content, detonation performance, and noncovalent interactions. The theoretically computed energetic properties of triazole-based macrocycles reveal high positive heats of formation (1507-2761 kJ/mol), oxygen balance (-88.8 to -22.8%), high densities (1.87-1.90 g/cm3), superior detonation velocities (8.41-9.52 km/s), pressures (26.64-40.55 GPa), acceptable impact sensitivity (27-40 cm), and safety factor (51-290). The overall energetic assessment highlights triazole-based macrocycles as a potential framework that will be useful for developing advanced energetic materials.

Computational Manifestation of Nitro-Substituted Tris(triazole): Understanding the Impact of Isomerism on Performance-Stability Parameters.

Density functional theory (DFT) methods were used to design a series of energetic dinitro-tris(triazole) isomers by altering the triazole rings and -NO2 groups. The impact of three nitrogen atoms' position in the tris(triazole) scaffold on energy content, performance, and stability was discussed. Based on computed heats of formation and densities, the detonation properties were predicted using the thermochemical EXPLO5 (v6.06) code. Using the bond dissociation energy of the longest C-NO2 bond, the thermal stability was investigated. The mechanical sensitivities were estimated and correlated with RDX and HMX using maximum heats of detonation (Q), free void (ΔV) in the lattice of the crystalline compound, and total -NO2 group charge. Among the designed series, compounds O4, R1, R3, and R4 display high heats of formation (>450 kJ/mol), high densities (>1.92 g/cm3), good detonation performances (D > 8.76 km/s and P > 32.0 GPa), and low sensitivities. Our findings suggest that the isomeric tricyclic triazole backbone could be a promising platform for developing new high-performing and thermostable energy materials.

Orientation and Alignment dynamics of polar molecule driven by shaped laser pulses.

We review the theoretical status of intense laser induced orientation and alignment-a field of study which lies at the interface of intense laser physics and chemical dynamics and having potential applications such as high harmonic generation, nano-scale processing and control of chemical reactions. The evolution of the rotational wave packet and its dynamics leading to orientation and alignment is the topic of the present discussion. The major part of this article primarily presents an overview of recent theoretical progress in controlling the orientation and alignment dynamics of a molecule by means of shaped laser pulses. The various theoretical approaches that lead to orientation and alignment such as static electrostatic field in combination with laser field(s), combination of orienting and aligning field, combination of aligning fields, combination of orienting fields, application of train of pulses etc. are discussed. It is observed that the train of pulses is quite an efficient tool for increasing the orientation or alignment of a molecule without causing the molecule to ionize. The orientation and alignment both can occur in adiabatic and non-adiabatic conditions with the rotational period of the molecule taken under consideration. The discussion is mostly limited to non-adiabatic rotational excitation (NAREX) i.e. cases in which the pulse duration is shorter than the rotational period of the molecule. We have emphasised on the so called half-cycle pulse (HCP) and square pulse (SQP). The effect of ramped pulses and of collision on the various laser parameters is also studied. We summarize the current discussion by presenting a consistent theoretical approach for describing the action of such pulses on movement of molecules. The impact of a particular pulse shape on the post-pulse dynamics is also calculated and analysed. In addition to this, the roles played by various laser parameters including the laser frequency, the pulse duration and the system temperature etc. are illustrated and discussed. The concept of alignment is extended from one-dimensional alignment to three-dimensional alignment with the proper choice of molecule and the polarised light. We conclude the article by discussing the potential applications of intense laser orientation and alignment.

Substituted triazolo-triazine derivatives as energetic materials: a computational investigation and assessment.

A series of energetic compounds were derived from [1,2,4]triazolo[1,5-a][1,3,5]triazine and azo-bridged fused backbone by introducing the -NO2, -NHNO2, -ONO2, -N3, and -NH2 explosophoric groups. The influence of explosophoric groups on energetic properties has been explored. All the compounds exhibit positive energy content (34.4-1955.4 kJ/mol) and densities (1.71-1.99 g/cm3) subject to fused triazole and triazine framework and various functional groups. The designed compounds with -NHNO2, -ONO2, and -NO2 functional groups possess high detonation velocities (8.23-9.00 km/s), pressures (30.94-37.68 GPa), Gurney velocities (2.70-2.88 km/s), and power index (109-131%) superior to TNT (6.94 m/s, 22.0 GPa, 2.37 km/s, and 118%) and comparable with RDX (8.60 km/s, 33.92 GPa, 2.93 km/s, and 169%) and HMX (8.90 km/s, 38.39 GPa, 2.97 km/s, and 169%). Based on high nitrogen and energy content, performance parameters, and sensitivity data, the designed compounds show high potential to be used as energetic materials. Graphical abstract.

Field-free molecular orientation by delayed elliptically polarised laser pulses.

A theoretical model of NAREX (non-adiabatic rotational excitation) and field-free molecular orientation by a short specific elliptically polarised laser pulses (EPLPs) driving a polar molecule is presented. By choosing the proper value of elliptically polarised field parameters, efficient field-free orientation could be achieved. It is demonstrated that NAREX can be controlled by various laser parameters, out of which pulse shape plays the most significant role. The effect of elliptic parameter on the rotational excitation and orientation dynamics is also under concern.

Effect of aligning pulse train on the orientation and alignment of a molecule in presence of orienting pulse.

Field-free molecular alignment is studied theoretically in presence of orienting laser pulse and a delayed Infrared laser (IRL) pulse train. The pulse shapes taken are sine square (sin2) and square. The degree of alignment can be significantly enhanced by the combination of orienting pulse and IRL pulse train compared with only IRL pulse train. Special emphasis is laid on time delay between orienting and aligning pulse, the width and shape of the pulse train. By adjusting the time delay, width and intensity of coupling laser one can suppress a population of particular state while simultaneously enhancing the population of desired states.

Adsorbed molecules in external fields: Effect of confining potential.

We study the rotational excitation of a molecule adsorbed on a surface. As is well known the interaction potential between the surface and the molecule can be modeled in number of ways, depending on the molecular structure and the geometry under which the molecule is being adsorbed by the surface. We explore the effect of change of confining potential on the excitation, which is largely controlled by the static electric fields and continuous wave laser fields. We focus on dipolar molecules and hence we restrict ourselves to the first order interaction in field-molecule interaction potential either through permanent dipole moment or/and the molecular polarizability parameter. It is shown that confining potential shapes, strength of the confinement, strongly affect the excitation. We compare our results for different confining potentials.