Strategy for Constructing Low-Sensitivity High-Energy Molecules by Combining N-oxidation and NO2/NH2 Substitution on Azole Rings

Modern computing systems require enhanced performance; however, the conventional memories such as Static Random Access Memory (SRAM) are inadequate to support this demand. This is mainly due to the fact that SRAM density cannot be increased commensurately with Complementary Metal-Oxide–Semiconductor (CMOS) transistor scaling. For example, typically the six-transistor (6T) SRAM, which has long been the workhorse of high-performance caches, requires a cell size of $120-200\mathrm {F} _{,}^{2}$ where F is the feature size [1]. On the other hand, Spin-Transfer Torque based Magnetoresistive Random-Access Memory (STT-MRAM) have emerged as universal memory technology due to its non-volatility, endurance, low operating voltages and ultrafast switching [2]. Further, they occupy much less area with 1T design comparable to DRAM with cell size of $6- 10 \mathrm {F}^{2}$ [1]. Thus, STT-MRAM is most suited for on-chip cache applications with highest possible density. One of the most important factors that determines the data retention time of STT-MRAM towards cache applications is the thermal stability of magnetization. It is known that with shrinking Magnetic Tunnel Junction (MTJ) dimensions, commensurate with CMOS scaling, the thermal stability of magnetization also decreases. This results in reduced retention times and increased bit error rates, posing significant challenges towards its application as cache memory. Hence, it is important to evaluate the thermal stability of magnetization as a function of decreasing MTJ diameter, to address their scalability and performance in advanced cache technology. In this article, we focus on perpendicular-MTJ and perform Micromagnetic simulations to evaluate the thermal stability factor at reduced MTJ diameter. Currently, the 22 nm nodes uses MTJ with 55–75 nm diameters [3]. First, we discuss the thermal energy barrier E b necessary for 7/21 days of data retention for L3-cache applications at different failure in time (FIT) rates. The requirement for the thermal energy barrier is given by: $\mathrm {E}_{b}=- ln[- ( \mathrm {t}_{0}/ \mathrm {t}_{p}) * ln(1 -$FIT$/ \mathrm {N}_{b})]$, where, FIT is failure in time, N b are no. of bits, $\mathrm {t}_{0}$ is the attempt frequency (assumed to be 1ns) and $\mathrm {t}_{p}$ is desired data retention time span (7/21 days). Figure 1 shows the calculated thermal energy barrier at different FIT's and data retention spans for various sizes of cache memories ranging between 1MB to 1GB. From this Figure, it is evident that the minimum thermal energy barrier should be greater than 20 KT for 1000 FIT's and 27 KT for 0.1 FIT's. Next, we calculate the thermal energy barrier of p-MTJ device to assess whether these demands can be satisfied with shrinking MTJ diameters. For this purpose, we use standard MTJ stack consisting of CoFeB as free layer with 0.85 nm thickness and its diameter varying between 5 – 60 nm to understand the scalability aspect. We perform E b calculations using a monodomain and domain wall assisted switching mechanism as mentioned in Ref. [2]. The thermal energy barriers are evaluated at three different values of temperature namely, $25 ^{\circ}\mathrm {C}($ room temperature), $100 ^{\circ}\mathrm {C}($ operational temperature) and $260 ^{\circ}\mathrm {C}($ solder reflow temperature). The required values, saturation magnetization (Ms), uniaxial anisotropy (Ks) and exchange constant (Aex) are used as measured in the GLOBALFOUNDRIES hardware [4]. Further, their temperature dependence is computed using Kinetic Monte Carlo simulations. The calculated thermal energy barriers, with varying MTJ diameters, are plotted in Figure 2 a). The MTJ diameters are varied between 5 – 60 nm which essentially encompasses 7, 10, 14 and 22nm CMOS technology nodes. The blue, red and green curves represent the data obtained at temperatures of 25, 100 and $260 ^{\circ}\mathrm {C}$, respectively. We observe that the lowest thermal barrier of approximately 30 KT can be achieved at 15 nm diameter for the highest solder reflow temperature. This implies that the MTJ diameter can be scaled down to 15 nm without compromising the thermal stability as required by 0.1 FIT's for 21 days. However, the energy barriers are drastically reduced below 15 nm diameter. Figure 2b) shows the switching efficiency figure of merit for p-MTJs, which is defined as the ratio of the energy barrier and switching current. Here, the critical switching current is calculated using the macrospin model described in Ref. [5]. From this plot it can be observed that the switching efficiency of MTJ saturates at smaller diameters. These diameter values, at which the switching efficiency saturates, reduces with increasing temperatures. In summary, we presented a comprehensive benchmarking of STT-MRAM for cache applications. The data shows that STT-MRAM is indeed scalable and can be integrated with advanced CMOS nodes. Our results clearly show that the thermal stability requirements for L3-cache can be met at even smaller MTJ diameters. Finally, the critical diameter at which the switching efficiency saturates is also dependent on temperature.

Developing high-energy materials that are powerful yet safe requires a careful balance between thermal stability, mechanical strength, and detonation performance. While metal coordination is a known strategy to improve the thermal stability of energetic compounds like trinitrophloroglucinol (TNPG), mono-metallic networks often suffer from diminished detonation performance and increased sensitivity. This work introduces a new class of hetero-metallic metal–organic networks, MM′-TNPG (M/M′ = Li, Na, K), that harmonizes all critical performance parameters, including enhanced thermal stability, reduced sensitivity, and high detonation output. Particularly, we present the first systematic correlation between mechanical properties evaluated via nanoindentation and detonation performance, revealing how structural features and metal coordination govern the material's robustness and energetic behavior. Correlating mechanical properties with the detonation and safety parameters could potentially offer a predictive approach to designing safer designs of high-performance, energetic materials. The hetero-metallic systems exhibit synergistic enhancement in mechanical strength without compromising explosive efficiency. This work introduces a novel design strategy for safer, high-performance, energetic materials, establishing a vital structural–mechanical–energetic property relationship that has previously been unexplored in this field.

Theoretical insights into effects of molar ratios on stabilities, mechanical properties and detonation performance of CL-20/RDX cocrystal explosives by molecular dynamics simulation

Simple molecular structures capable of emitting over the entire visible range are still a challenge. Planar molecular structures have the drawback of fluorescence quenching in the solid state thus limiting their application fields. Combining long range excimer/exciplex emissions with a compound emission have been used to get white light. In this work, a series of new coumarin derivatives having a planar structure have been synthesized and characterized. The effects of systematic variation in alkyl chain functionalization providing morphological variations that permit interesting solid state emitting properties have been discussed simultaneously with electrochemical behavior and OLED (organic light emitting diode) device applications. Carbon chains containing 0–16 carbon atoms have been studied in order to conclude the results that systematic changes in alkyl group substitution can be utilized as a tool to tune the emitting color of these planar coumarins. Alkyl chains were introduced by O-acylation and O-benzoylation reaction on the hydroxyl group of parent coumarin 5. Thus the present strategy is also helpful in establishing a template to control the unproductive interchromophore electronic couplings. Solid state fluorescence properties support the crystal studies. Theoretical studies are also in agreement with experimental data. Electroluminescence of Device 2 with a turn on voltage (Von) around 5–6 V having s-CBP doped with 1% of 8 having alkyl substitution of 2-carbons is found to exhibit white emission with CIE co-ordinates of (0.29, 0.34) which is close to white emission while the alkyl substitution of 14-carbons (compound 17) in Device 7 (Von = 7 V) exhibited green emission. Thus a strategy helpful to tune the electroluminescence has been discussed.

Using wide-range variable angle spectroscopic ellipsometry, the authors demonstrate large optical uniaxial anisotropy of vacuum-deposited organic amorphous films of hole and electron transport materials having long or planar molecular structures. The ordinary refractive indices and extinction coefficients were higher than the extraordinary ones, revealing that the molecules in the amorphous films are horizontally oriented. The horizontal orientation requires significant modifications in the understanding of both the electrical and optical characteristics of amorphous films when we use materials having long or planar molecular structures.

Multi-resonance thermally activated delayed fluorescence (MR-TADF) emitters hold great potential for applications in organic light-emitting diodes (OLEDs). However, owing to their inherently rigid and planar molecular structures and the localized charge transfer (LCT) characteristics, these emitters typically exhibit poor solubility and low reverse intersystem crossing (RISC) rates, which are unfavorable for high-performance solution-processed OLEDs. Herein, we constructed three U-shaped MR-TADF emitters (BN-N-TTz, BN-N-PCz and BN-N-BN) by introducing triazine, phenylcarbazole and MR-TADF units at the 1- and 8-positions of a naphthalene ring. This U-shaped molecular architecture endows the emitters with excellent solubility. Moreover, this structure not only enhances spin-orbit coupling between the S1 and T1 states but also reduces the energy difference between the two states (ΔE ST), thereby increasing RISC rates to as high as 3.17 × 105 s-1. Notably, the solution-processed OLED based on BN-N-BN achieved the highest EQE of 27.6% without sensitizers. This represents one of the best performances among solution-processed OLEDs based on MR-TADF emitters to date. This simple approach reveals the great potential for developing solution-processable emitters suitable for high-performance rigid and planar molecular structures.

Nine different nitrated phenyl peroxy anhydrides were synthesized using two different strategies and crystal structures of two compounds were determined. Sensitivities of the compounds toward impact, friction and electrostatic discharge were measured and the thermal stability was determined. Some of the compounds are remarkable insensitive and they show relatively high thermal decomposition points for organic peroxides. Detonation parameters and performance data were calculated using the EXPLO5 program yielding performance values in the range of trinitrotoluene (TNT).

Two dimers (2 and 3), dendritic tetramer (4), hexamer (5), and decamer (6) of benzo[1,2-b:3,4-b':5,6-b'']trithiophene (BTT), a potential π-core unit with C(3h) symmetry, were synthesized, characterized, and evaluated for possible use as organic semiconductors. Single crystal X-ray analyses of the dimers (2 and 3) revealed that they have planar molecular structures with dihedral angles of almost 180° between two BTT units. In accordance with the rigid and planar molecular structure, the unsubstituted dimer (2) is poorly soluble, whereas the octyl-substituted dimer (3) has improved solubility. Although the solubility of the dendritic tetramer (4) is decreased, further extended systems, i.e., the dendritic hexamer (5) and decamer (6), have solubilities better than that of 4. With increasing numbers of BTT units in the molecule, the experimentally determined energy levels of HOMO shift upward slightly and the HOMO-LUMO energy gaps become smaller, but the extent of HOMO destabilization and reduction of the HOMO-LUMO gap are not significant. Taking into account the energy levels of the frontier orbitals, 3-6 could be useful as p-channel organic semiconductors rather than n-channel. In fact, the spin-coated thin film of 3 with edge-on molecular orientation acted as an active channel of field-effect transistors that showed hole mobilities as high as 0.14 cm(2) V(-1) s(-1), indicating that the BTT core is a useful π-conjugated system for application to organic semiconductors, although 4-6 gave FET characteristics rather inferior to those of 3, owing to their amorphous nature in the thin film state.

A series of isomers of tetranitro-bis-1,2,4-triazoles were designed, and their electronic structures, heats of formation, densities, detonation performances, thermal stabilities, and impact sensitivities were investigated by density functional theory (DFT). The structure and energetic properties of 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX) were also calculated at the same level. On comparing with the detonation velocity and pressure and bond dissociation energy (BDE) of HMX, it was found that four isomers (BT2, BT5, BT6, BT7) have higher detonation performances than HMX and three isomers (BT5, BT6, BT7) have better thermal stabilities than HMX. The calculated results of impact sensitivities indicated that all of the designed isomers have more sensitivity than HMX. The calculated results of energy gaps between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) indicated that all of the designed isomers were more easily excited than HMX in the chemical reaction process. In particular, 3,3′,5,5′-tetranitro-1,1′-bis-1,2,4-triazoles (BT5) exhibited excellent detonation performances (9464 m s–1, 39.44 GPa) and good thermal stability (BDE 256.81 kJ mol–1). The results indicated that the isomerization of tetranitro-bis-1,2,4-triazoles could improve their detonation performance or thermal stability and might lead to a promising isomer possessing both good performance and high thermal stability.

3,4-Bisnitrofurazanfuroxan (DNTF) is a typical high energy density compound (HEDC), it has high crystal density and detonation parameters, but also high mechanical sensitivity. To decrease its mechanical sensitivity, the DNTF based polymer bonded explosives (PBXs) was designed. The pure DNTF crystal and PBXs models were established. The stability, sensitivity, detonation performance and mechanical properties of DNTF crystal and PBXs models were predicted. Results show that PBXs models containing fluorine rubber (F2311) and fluorine resin (F2314) have higher binding energy, meaning that DNTF/F2311 and DNTF/F2314 is relatively more stable. PBXs models have higher value of cohesive energy density (CED) than pure DNTF crystal, DNTF/F2311 and DNTF/F2314 have the highest value of CED, implying that the sensitivity of PBXs is effectively decreased, DNTF/F2311 and DNTF/F2314 is more insensitive. PBXs have lower crystal density and detonation parameters than DNTF, the energy density is declined, DNTF/F2314 has higher energetic performance than other PBXs. Compared with pure DNTF crystal, engineering moduli (tensile modulus, shear modulus, bulk modulus) of PBXs models are obviously decreased, but Cauchy pressure is increased, implying that the mechanical properties of PBXs is superior to pure DNTF component, the PBXs containing F2311 or F2314 have more preferable mechanical properties. Consequently, DNTF/F2311 and DNTF/F2314 have the best comprehensive properties and is more attractive among the designed PBXs, indicating that F2311 and F2314 are more advantageous and promising in ameliorating properties of DNTF. The properties of DNTF crystal and PBXs models were predicted through molecular dynamics (MD) method under Materials Studio 7.0 package. The MD simulation was performed with isothermal-constant volume (NVT) ensemble, and the force field was chosen as COMPASS force field. The temperature was set as 295K, the time step was 1fs and the total MD simulation time was 2ns.

Nitration of 3-amino-4-nitrofurazan with N2O5 yielded the corresponding nitramine. 3-Nitramino-4-nitrofurazan is a very promising explosive regarding detonation performance but it suffers from its hygroscopicity, low thermal stability, and high sensitivity to external stimuli. The introduction of other nitramine groups either by alkylation with 1-chloro-2-nitrazapropane or by combination of two 3-nitramino-4-nitrofurazans yielded the corresponding more stable and non-hygroscopic open-chain nitramines. Their molecular structures were investigated by single-crystal X-ray diffraction. The remarkable difference of their impact sensitivities were evaluated by calculation of their electrostatic potential of the molecular surfaces. Furthermore, the detonation parameters and combustion parameters of the open-chain nitramines were computed with the EXPLO5 (v. 6.02) computer code.

In this paper, we model and investigate the impact of Row Hammering (RH) on Spin-Transfer Torque RAM (STTRAM) by exploiting its write operation. STTRAM suffers from high write current and long write latency which can result in ground bounce. The magnitude of the bounce depends on the old data and the new data that is being written. The bounce can propagate to the nearest word-line drivers and partially turn ON the access transistors making weak current flow through the memory bitcells and reducing their thermal energy barrier. Therefore, continuous write at a particular location can force the massive number of unselected bits to suffer from degraded thermal barrier due to weak RH current. Reduced thermal barrier may lead to retention failures and make the bits sensitive to stray magnetic field/thermal noise. Those bits can also suffer from read disturb if they are read. These issues could be even worse for Short Retention NVM (SRNVM) which is suitable for Last Level Cache (LLC) and has a base retention of only few seconds. The ground bounce can also propagate to bitline/ source-line drivers and the selected cells will experience lower headroom voltage. This will lead to read failure (due to degraded sense margin) and write failure (due to increased write latency). Simulation result indicates that RH attack can flip the bits in just 30.84secs for STTRAM with base retention of 1 min. In presence of elevated temperature, the retention time can be further reduced to 2.46secs and 0.19secs for T=50C and T=75C respectively. RH attack can increase read disturb by 2.09X for bitcell with 1min base retention at T=25C. Simulation result also indicates that RH attack can cause read/write failure if the bitcell being read/written experience 306mV (for data 0)/110mV (for writing 0 –> 1) of bounce. To the best of our knowledge, this is the first RH attack study for STTRAM-based cache.

N,N'-linked bis-1,2,4-trizaoles compounds substituted with different groups such as -NH2, -NO2, -NHNO2, -OH and -CH(NO2)2 were designed and studied by density functional theory (DFT) at B3LYP/6-311+G(2df, 2p) level. The calculated results of heats of detonation, detonation velocities, detonation pressures, bond dissociation energy and impact sensitivity (h50) indicated that -NO2, -NHNO2 and -CH(NO2)2 groups play an important role in elevating the detonation performances of designed compounds, and -NO2 group play an important role in elevating the thermal stability of designed compounds, and the designed compounds with -NO2 and -NHNO2 groups were less sensitivity than that of -CH(NO2)2 group. The calculated detonation performances, thermal stability and impact sensitivity of designed compounds were compared with those of some classical explosives such as 1,3,5-trinitro-1,3,5-triazinane (RDX) and 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX). The computed results show that 3,5,3'-trinitro-4,4'-bis-1,2,4-triazoles (B3) possess higher detonation performances and thermal stability than that of RDX, but more sensitivity than that of RDX; 3,5,3',5'-tetradinitromethyl-4,4'-bis-1,2,4-triazoles (E4) possess higher detonation performances than that of RDX, but lower thermal stability and more sensitivity than that of RDX; 3,5,3',5'-tetranitro-4,4'-bis-1,2,4-triazoles (B4) possess higher detonation performances and thermal stability than that of HMX, but more sensitivity than that of HMX; 3,5,3',5'-tetranitramine-4,4'-bis-1,2,4-triazoles (C4) possess higher detonation performances than that of HMX, and similar sensitivity to HMX, but lower thermal stability than that of and HMX.

N-N=N-N]-linked fused triazoles with π-π stacking and hydrogen bonds: Towards thermally stable, Insensitive, and highly energetic materials

Computational studies on the heats of formation, energetic properties, and thermal stability of energetic nitrogen-rich furazano[3,4-b]pyrazine-based derivatives