Characteristic Activation Energy Research Articles

Reignition characteristics of lignite affected by pre-oxidation and liquid nitrogen cold soaking

The propensity of residual oxidized coal to be reignited within enclosed fire areas in coal mines under liquid nitrogen (LN2) cold soaking remains unclear. Therefore, scanning electron microscopy (SEM), low-temperature nitrogen adsorption (LTNA), and thermogravimetric (TG) experiments were conducted to characterize the pore structure and secondary oxidation of oxidized cold-soaked coal. The results indicate that pre-oxidation or cold soaking alone can promote the generation and merging of pores and make the pore structure more complex, especially when pre-oxidized. However, pore evolution is suppressed and then improves when lignite is simultaneously subjected to pre-oxidation and cold soaking. In particular, the macropore volume and specific surface area decrease and then increase. The cryogenic shrinking of the LN2 results in the collapse of the loose coal matrix, which subsequently blocks the macropores. In contrast, vaporization expansion enhances pore connectivity with continuous LN2 injections, transforming mesopores into macropores, especially in the pore ranges of 2–5 nm and >50 nm. Additionally, pre-oxidation or cold soaking alone improves the oxidizing activity and combustion performance of raw coal. However, continuous cold soaking initially increases and subsequently decreases the characteristic temperatures and activation energy of oxidized coal. Oxidization at 200 °C with one cold soaking can further lower reignition propensity. The average activation energy of oxidized coal decreases by 22.9%–29 % when soaked more than three times. The improvement in combustion property is closely related to the increasing number of macropores because a larger pore volume and specific surface area are conducive to oxygen diffusion and adsorption. Therefore, pre-oxidation and cold soaking promote and inhibit the reignition of coal when performed simultaneously. These results provide theoretical guidance for rational liquid-nitrogen injection to control coal fires.

Comparative investigation of low temperature oxidized and pyrolyzed cokes from the inferior heavy oil: Structural feather, thermo-oxidation behavior, and kinetics

It was crucial to study the low temperature coking process for the heavy oil, which affected the fuel availability and subsequent in-situ combustion progress. From this perspective, low temperature coking experiments with different atmospheres were accomplished for the inferior heavy oil to obtain oxidized (cokeLTO) and pyrolytic (cokeLTP) cokes, which were further employed to trace structural feathers via joint analysis of elemental analysis, Fourier transform infrared spectrophotometry (FTIR) and X-ray photoelectron spectroscopy (XPS) spectra, and to characterize thermo-oxidative characteristics and kinetics via different thermal analyses (TG-DTG/DSC) and model-free methods. The results showed that a relatively less aliphatic and more aromatic structures were contained in cokeLTO with a relatively higher proportion of C-O, C = O, O-C = O groups and C/H ratio, implying that oxygen atom was served as the promoter to replace hydrogen atom and accelerate macromolecular structure formation. While the decomposition and conversion of N- and S- functional groups were complicated and insensitive to the coking atmosphere. Furthermore, cokeLTO had a more dominant thermo-oxidation behavior than cokeLTP with better exothermic characteristic and lower activation energy distribution. From this study, it could provide a vital piece of updated insights on the role of low temperature oxidation process in coke deposition and feature.

Study of electric-field induced ionic migration on all-inorganic perovskite CsPbBr3 single crystal nuclear radiation detector

As one of the promising room temperature nuclear radiation detection materials, the all-inorganic perovskite CsPbBr3 single crystal has been receiving much attention in recent years. Even though the performance of the CsPbBr3 detector is improving continuously, the disadvantages of detection instability have not been solved fundamentally, and this instability is mainly caused by ionic migration in the CsPbBr3 single crystal itself. In this paper, a reasonable ionic migration model is proposed based on an in-depth study of the current hysteresis phenomenon and ionic migration mechanism in the Ti/CsPbBr3/Ti detector. The model shows that the ions migrate to the anode or cathode under an external electric field, and the accumulated ions subsequently form an inverted internal electric field inside the crystal and carrier transport barriers at the metal–semiconductor interface simultaneously. The photoelectric characteristic and ionic migration activation energy (Eaion) fitting results also prove the rationality of the ionic migration model. Furthermore, the ionic migration model can also be used to explain the left-shift of the energy response peak and the decrease in the normalized charge collection efficiency in the Ti/CsPbBr3/Ti detector. This paper systematically investigates the intrinsic origin of migrated ions and the influence of ionic migration on detection stability, which will provide a potential solution to improve detection stability by suppressing ionic migration in the near future.

Tuning Non-Isothermal Crystallization Kinetics between Fe20Co20Ni20Cr20(P0.45B0.2C0.35)20 High-Entropy Metallic Glass and the Predecessor Fe75Cr5P9B4C7 Metallic Glass

In the present work, comparisons of non-isothermal crystallization kinetics between Fe20Co20Ni20Cr20(P0.45B0.2C0.35)20 high-entropy metallic glass (HEMG) and the predecessor Fe75Cr5P9B4C7 metallic glass (MG) were performed with X-ray diffraction and differential scanning calorimetry approaches. The HEMG possesses a harsher crystallization process compared with the predecessor MG, deriving from a higher triggering energy for all the characteristic transitions and local activation energy along with a smaller local Avrami exponent and a growth with pre-existing nuclei. Meanwhile, the glass transition is the easiest process, but the nucleation of the second crystallization case is the hardest transition for the HEMG. However, the predecessor MG possesses distinctly different crystallization features of a moderate difficulty for the glass transition, the harshest process for the growth transition of the second crystallization case, and a crystallization of growth with a diverse nucleation rate. These results conclusively prove that the non-isothermal crystallization kinetics can be significantly changed after the present high-entropy alloying with the substitution of similar solvent elements Co, Ni, and Cr with Fe in Fe75Cr5P9B4C7 MG. Moreover, the two alloys possess a strong glassy formation melt with high thermal stability and diverse crystallized products after non-isothermal crystallization.

Complexity of temperature dependence in methanogenic microbial environments.

There is virtually no environmental process that is not dependent on temperature. This includes the microbial processes that result in the production of CH4, an important greenhouse gas. Microbial CH4 production is the result of a combination of many different microorganisms and microbial processes, which together achieve the mineralization of organic matter to CO2 and CH4. Temperature dependence applies to each individual step and each individual microbe. This review will discuss the different aspects of temperature dependence including temperature affecting the kinetics and thermodynamics of the various microbial processes, affecting the pathways of organic matter degradation and CH4 production, and affecting the composition of the microbial communities involved. For example, it was found that increasing temperature results in a change of the methanogenic pathway with increasing contribution from mainly acetate to mainly H2/CO2 as immediate CH4 precursor, and with replacement of aceticlastic methanogenic archaea by thermophilic syntrophic acetate-oxidizing bacteria plus thermophilic hydrogenotrophic methanogenic archaea. This shift is consistent with reaction energetics, but it is not obligatory, since high temperature environments exist in which acetate is consumed by thermophilic aceticlastic archaea. Many studies have shown that CH4 production rates increase with temperature displaying a temperature optimum and a characteristic apparent activation energy (Ea). Interestingly, CH4 release from defined microbial cultures, from environmental samples and from wetland field sites all show similar Ea values around 100 kJ mol-1 indicating that CH4 production rates are limited by the methanogenic archaea rather than by hydrolysis of organic matter. Hence, the final rather than the initial step controls the methanogenic degradation of organic matter, which apparently is rarely in steady state.

Electronic transport mechanisms in a thin crystal of the Kitaev candidate α -RuCl3 probed through guarded high impedance measurements

α-RuCl3 is considered to be the top candidate material for the experimental realization of the celebrated Kitaev model, where ground states are quantum spin liquids with interesting fractionalized excitations. It is, however, known that additional interactions beyond the Kitaev model trigger in α-RuCl3 a long-range zigzag antiferromagnetic ground state. In this work, we investigate a nanoflake of α-RuCl3 through guarded high impedance measurements aimed at reaching the regime where the system turns into a zigzag antiferromagnet. We investigated a variety of temperatures (1.45–175 K) and out-of-plane magnetic fields (up to 11 T), finding a clear signature of a structural phase transition at ≈160 K as reported for thin crystals of α-RuCl3, as well as a thermally activated behavior at temperatures above ≈30 K, with a characteristic activation energy significantly smaller than the energy gap that we observe for α-RuCl3 bulk crystals through our angle resolved photoemission spectroscopy (ARPES) experiments. Additionally, we found that below ≈30 K, transport is ruled by Efros–Shklovskii variable range hopping (VRH). Most importantly, our data show that below the magnetic ordering transition known for bulk α-RuCl3 in the frame of the Kitaev–Heisenberg model (≈7 K), there is a clear deviation from VRH or thermal activation transport mechanisms. Our work demonstrates the possibility of reaching, through specialized high impedance measurements, the thrilling ground states predicted for α-RuCl3 at low temperatures in the frame of the Kitaev–Heisenberg model and informs about the transport mechanisms in this material in a wide temperature range.

Study on evolution characteristics of thermal contribution functional groups in low temperature oxidation process of bituminous coal

In order to study the key functional groups that play a major role in heat during the low-temperature oxidation of bituminous coal, this paper takes three kinds of bituminous coals with different degrees of metamorphism as the research objects, analyzes the variation law of thermal effect parameters during low-temperature oxidation of coal by C80 microcalorimetry experiment, and calculates and analyzes the activation energy of different oxidation stages by oxidation kinetics method. The change rule of functional groups during low temperature oxidation was analyzed by Fourier transform infrared experiment. The correlation between heat and functional groups was comparatively analyzed by using the grey correlation degree and frequency ratio model method, and the key functional groups of bituminous coal that play a major role in heat at different oxidation stages were identified. The results showed that with the deepening of metamorphism degree, the heat flow curve and exotherm gradually decrease, while the characteristic temperature and activation energy gradually increase. Among them, from Caojiatan's long-flame coal to Dongtan's gas coal, the exotherm decreased by 35.5 %, and the maximum endothermic rate temperature and heat balance temperature increased by 3.43 °C and 13.32 °C respectively. With the deepening of metamorphism degree, the content of hydroxyl groups keeps increasing, the content of aliphatic hydrocarbons, aromatic functional groups and fatty ethers first decreases and then increases, and the content of carboxyl groups first increases and then decreases. The correlation analysis between the gray correlation method and the frequency ratio model method shows that as the degree of metamorphic deepened, the key functional groups that play a major role in heat change from COOH to OH in the rapid endothermic stage, from-CH2- to COC in the slow endothermic stage, and from OH to COOH in the rapid exothermic stage. The key functional groups of bituminous coal, which play a major role in heat, follow the evolution of OH → CH2, COC → COOH as the oxidation stage advances.

Analysis of the Catalytic Effects Induced by Alkali and Alkaline Earth Metals (AAEMs) on the Pyrolysis of Beech Wood and Corncob

The catalytic pyrolysis of beech wood and corncob was experimentally investigated considering six additives containing alkali and alkaline earth metals (Na2CO3, NaOH, NaCl, KCl, CaCl2 and MgCl2). Thermogravimetric analyses (TGA) were carried out with raw feedstocks and samples impregnated with different concentrations of catalysts. In a bid to better interpret observed trends, measured data were analyzed using an integral kinetic modeling approach considering 14 different reaction models. As highlights, this work showed that cations (Na+, K+, Ca2+, and Mg2+) as well as anions (i.e., CO32−, OH−, and Cl−) influence pyrolysis in selective ways. Alkaline earth metals were proven to be more effective than alkali metals in fostering biomass decomposition, as evidenced by decreases in the characteristic pyrolysis temperatures and activation energies. Furthermore, the results obtained showed that the higher the basicity of the catalyst, the higher its efficiency as well. Increasing the quantities of calcium- and magnesium-based additives finally led to an enhancement of the decomposition process at low temperatures, although a saturation phenomenon was seen for high catalyst concentrations.

Thin film rheology via focused laser spike thermocapillary dewetting

Focused laser spike (FLaSk) dewetting employs a localized heat source to create thermocapillary-induced trench-ridge morphologies. Using a universal heating substrate coupled with optical microscopy, we have studied the dewetted ridge feature for several distinct thin films of glass-forming materials. The evolution of the ridge’s radius over time can be modeled to derive a maximum dewetted radius and a characteristic decay time. The decay time shows an Arrhenius behavior when compared to the mean melt pool temperature, leading to a characteristic activation energy. An effective viscosity can also be defined. These descriptors demonstrate FLaSk’s potential for rapid metrology.

Atomistic simulations of [formula omitted]Ar diffusion in muscovite

Muscovite ranks among the most commonly dated minerals in 40Ar/39Ar geochronology. Yet, its use in thermochronological reconstructions is hampered by the lack of reliable data on its 40Ar diffusional behavior. In this contribution, we investigate 40Ar lattice diffusion in muscovite at the atomic scale using Molecular Dynamics (MD) simulations combined with Nudged Elastic Band (NEB) and Transition State Theory (TST). Classical MD simulations of 40Ar recoil dynamics in 2M1 muscovite reveal that 40Ar initially resides predominantly in the interlayer region, close to its production site. Systematic computations of migration barriers coupling NEB with TST identify the divacancy mechanism as the more energetically favorable pathway for 40Ar diffusion in the interlayer region, with characteristic activation energy E=66 kcal.mol−1 and frequency factor D0=6×10-4 cm2.s−1. For typical cooling rates between 1–100 °C.Ma−1 and grain size varying from 0.1 and 1 mm, these parameters predict closure temperatures significantly higher (∼ 200 °C) than currently accepted maximum estimates (∼ 500 °C). Consistent with long-standing empirical evidence, our theoretical results downplay the role of purely thermally activated diffusion in promoting efficient 40Ar transport in ideal (stoichiometrically stable and undefective) muscovite. Along with experimental and field-based evidence, they call for more complex physics to explain the 40Ar retention properties of natural muscovite, most notably by considering crystal-chemical disequilibrium interactions and the reactivity of the interlayer with the external medium.

Characterization and Performance Testing of an Intumescent Nanoinhibitor for Inhibiting Coal Spontaneous Combustion.

Considering disadvantages such as the low thermal stability and environmental pollution of existing gel inhibitors, a green and stable intumescent nanoinhibitor (INI) was prepared and tested. First, polyacrylamide (PAM), nano-silica, and intumescent flame retardant (IFR) were selected as raw materials. The INI was prepared by nanoparticle modification and cross-linking polymerization. Then, the structure and physical properties of INI were tested by Fourier transform infrared spectroscopy, scanning electron microscopy, and rheological experiments. Meanwhile, the inhibition performance of INI was studied through thermogravimetric analysis-Fourier transfer infrared spectroscopy (TGA-FTIR) analysis. The results suggest that the nanomodification improved the dispersibility of INI particles. The addition of modified nano-silica (MNS) and IFR enhances the strength of the reticular structure, thereby improving the transport convenience and covering ability of the INI gel. At high temperatures, IFR can generate a porous foamed carbon layer that further coats the coal. After INI inhibition treatment, the characteristic temperature and activation energy of coal were significantly improved, and the production of carbon monoxide and carbon dioxide decreased. Hence, irrespective of physical properties, physical inhibition performance, or chemical inhibition performance, INI performed well. Research results can provide valuable references for the preparation and performance study of a coal spontaneous combustion inhibitor.

Comparison of the charge-crystal and charge-glass state in geometrically frustrated organic conductors studied by fluctuation spectroscopy

We present a systematic investigation of the low-frequency charge carrier dynamics in different charge states of the organic conductors $\theta$-(BEDT-TTF)$_2$$M$Zn(SCN)$_4$ with $M$=Rb,Tl, which result from quenching or relaxing the charge degrees of freedom on a geometrically frustrated triangular lattice. Due to strong electronic correlations these materials exhibit a charge-ordering transition, which can be kinetically avoided by rapid cooling resulting in a so-called charge-glass state without long-range order. The combination of fluctuation spectroscopy and a heat pulse method allows us to study and compare the resistance fluctuations in the low-resistive quenched and the high-resistive charge-ordered state, revealing striking differences in the respective noise magnitudes. For both compounds, we find strongly enhanced resistance fluctuations right at the metal-insulator transition and a broad noise maximum in the slowly cooled charge-crystal state with partly dominating two-level processes revealing characteristic activation energies.

Effect of Ho Addition on the Glass-Forming Ability and Crystallization Behaviors of Zr54Cu29Al10Ni7 Bulk Metallic Glass.

The effect of holmium (Ho) addition on the glass-forming ability (GFA) and crystallization behaviors of Zr54Cu29Al10Ni7 bulk metallic glass (BMGs) were studied by employing differential scanning calorimetry (DSC), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The characteristic temperatures and activation energies of crystallization were obtained from DSC data. Classical kinetic modes were used to evaluate the crystallization processes of Zr54Cu29Al10Ni7 and Zr48Cu29Ni7Al10Ho6 BMGs. The results showed that Ho addition reduces the activation energy in the original crystallization period of Zr-based BMG and improves the nucleation, which is due to the formation of simpler compounds, such as CuZr2, Cu2Ho, and Al3Zr5.

Reactive Sintering of Dysprosium-Iron Garnet via a Perovskite-Hematite Solid State Reaction and Physical Properties of the Material.

In this paper, we report on a successful synthesis of dysprosium iron garnet Dy3Fe5O12 (DyIG) by a reactive synthesis method involving dysprosium iron perovskite and hematite. Phase formation was traced using dilatometry, and XRD measurements attested to the formation of the desired structure. Samples with relative density close to 97% were fabricated. The samples were characterized using vibrating sample magnetometry, dielectric spectroscopy, and UV-Vis-NIR spectroscopy. Magnetic properties were probed in temperatures between 80 and 700 K with a maximum applied field of 1 kOe. The measurements revealed several effects: the compensation of magnetic moments at a certain temperature, the inversion of the magnetocaloric effect, and the ability to measure the Curie temperature of the material. Activation energy was determined from UV-Vis-NIR and dielectric spectroscopy measurements. Characteristic magnetic temperatures and activation energy values of the samples were similar to bulk DyIG obtained using other methods.

Multi-functional epoxy vitrimers: Controllable dynamic properties, multiple-stimuli response, crack-healing and fracture-welding

Vitrimers, a new generation of polymeric materials, have been widely investigated to resolve the intersection of thermoplastics and thermosets, relying on the exchange reactions in networks. However, it is still a challenge to develop multi-functional vitrimer materials. Herein, multi-functional epoxy vitrimers that exhibited controllable dynamic properties, multiple-stimuli response, crack-healing and fracture-welding were prepared by introducing Fe3O4 nanoparticles into the networks of dual dynamic epoxy vitrimers. It was revealed that the typical dynamic parameters of vitrimer including the characteristic relaxation time (τ), activation energy (Ea), Arrhenius prefactor (τ0) and topology freezing transition temperature (Tv) could be readily adjusted in the multi-functional epoxy vitrimers. Moreover, the multi-functional epoxy vitrimers were simultaneously responsive to temperature, near infrared and magnetic field, while they could be driven by magnets, heated by near infrared and healed or welded by heating. Upon heating or near infrared, the cracks in samples could be successfully healed. Besides, by the cooperation of heating and magnet or near infrared and magnet, the multi-functional epoxy vitrimers were able to achieve non-touch welding of factures. These multi-functional epoxy vitrimers might have potential application in improving the reliability and extending the lifetime of polymeric materials. Meanwhile, the facile way to functionalize the epoxy vitrimers is estimated to be suitable for other vitrimer materials.

Coarsening kinetics of lamellar and equiaxed microstructures of eutectic Au–20Sn during the annealing

In this study, the microstructural evolution and coarsening kinetics of lamellar and equiaxed microstructures of eutectic Au–20Sn alloy during the annealing at 160–220 °C were systematically investigated. The lamellae and near-equiaxed grains coarsened strongly depending on the annealing temperature and holding time. Specifically, a higher annealing temperature effectively accelerated the coarsening process. Quantitative evaluations of lamellar and near-equiaxed coarsening kinetics of eutectic Au–20Sn alloy were performed respectively. The coarsening mechanisms for these two microstructures of eutectic Au–20Sn alloy were also discussed. During the annealing, the lamellar coarsening kinetics of eutectic Au–20Sn was described as λ 2 - λ 0 2 = K L t with the characteristic activation energy Q about 116.64 kJ mol −1 . The lamellar coarsening behavior was dominantly controlled by the fault migration and annihilation aroused from the interfacial diffusion of Sn atoms. The near-equiaxed grain coarsening followed the Lifshitz-Slyosov-Wagner theory r n - r 0 n = K MLSW t with temporal exponent n = 4 at 180 °C and n = 5 at 220 °C, respectively. The near-equiaxed grain coarsening was controlled by grain-boundary diffusion. This study provided a microstructural evolution law for eutectic Au–20Sn alloy, and it further offers a theoretical basis for the deformation processing during the thermal processes.

PEM Single Cells under Differential Conditions: Full Factorial Parameterization of the ORR and HOR Kinetics and Loss Analysis

The anode and cathode kinetics are parameterized based on differential cell measurements. Systematic parameter variations are evaluated to disentangle the dependencies of the electrochemical impedance spectroscopy (EIS) signatures in H2/H2 mode. We introduce a new CO recovery protocol for both electrodes that enables to accurately characterize the hydrogen oxidation reaction (HOR) kinetics. Then, we demonstrate that a compact Tafel kinetics law captures the oxygen reduction reaction (ORR) kinetics for a full factorial grid of conditions, covering a wide range of relative humidities (rH), temperatures, oxygen partial pressures and current densities. This yields the characteristic activation energy and effective reaction order, and we reconcile models that make different assumptions regarding the rH dependency. Moreover, we analyze O2 transport contributions by steady-state and transient limiting current techniques and heliox measurements. Although the rising uncertainty of loss corrections at high current densities makes it impossible to unambiguously identify an intrinsic potential-dependent change of the Tafel slope, our data support that such effect needs not be considered for steady-state cathodic half-cell potentials above 0.8 V.

Disentangling diffusion heterogeneity in high-entropy alloys

Diffusion in the traditional single-crystalline solids is usually dynamically homogeneous characterized by a single-value or two characteristic activation energies. However, such a scenario breaks down at atomic-scale in the recently advanced high-entropy alloys, which are of unique structural features with multi-principal elements randomly occupying on lattice sites that induces strikingly local chemical heterogeneity. Here we uncover and decouple the possible dynamic heterogeneity accommodating the lattice diffusion in an archetypical high-entropy Cantor alloy CoCrFeMnNi via combined molecular statics, molecular dynamics, and a saddle-point sampling method. Wide distribution of vacancy formation energies and migration energies are revealed. We propose a single-vacancy and a vacancy-saturated model, respectively, to set up possible lower bound and upper bound of diffusivities. The models define a possible range of activation energies for the lattice diffusion in high-entropy alloys, which are comparable to experimental data. Finally, we argue that the conventional hypothesis of diffusion activation energy estimated from Arrhenius equation as the sum of the vacancy formation energy and migration energy becomes intractable in high-entropy alloys. These atomic-scale insights into diffusion heterogeneity, in contrast to the classical theory of homogeneous diffusion in conventional solid solutions, highlight the complexity of diffusion pathways and the intimate correlation between chemical, topological disorder and dynamic heterogeneity in the generic complex concentrated alloys.

Renewable furan-derived diamine as primary amine source to prepare fully bio-based bis-benzoxazine monomer under solvent-free condition

Fully bio-based benzoxazine is classified into sustainable high-performance thermosetting resin and has become current focus in polybenzoxazine field. But lack of bio-based primary diamine restricted the preparation of bis-benzoxazine with high biomass content. In this report, renewable furan-containing diamine (PDFA) derived from furfurylamine was condensed with cardanol/eugenol and formaldehyde under solventless condition to obtain two biomass-based bis-benzoxazine monomers of BBOZ-Ca and BBOZ-Eu. The curing behaviors of two monomers were investigated by non-isothermal DSC method and the results showed that BBOZ-Ca possessed broad processing window comparing with BBOZ-Eu, the characteristic polymerization temperature and activation energy of two monomers were very close to each other, but the total heat releasing (enthalpy of polymerization) of BBOZ-Eu was higher than that of BBOZ-Ca due to its high oxazine content. The TGA results indicated that cured BBOZ-Eu had better thermal resistance than cured BBOZ-Ca, the char yield of cured BBOZ-Eu was 65.4% at 850 °C. Copolymerization with BBOZ-Eu effectively increased the char yield of cured BBOZ-Ca. Isothermal DMA was utilized to further investigate the curing kinetics and the results showed that the storage modulus increased rapidly when polymerization was initiated. The surface properties of cured films were studied using scanning electron microscope (SEM) images and contact angle measurement.

Исследование с помощью молекулярной динамики образования димеров на поверхности (001) GaAs при низких температурах

The simulation of dimers formation during the low-temperature reconstruction of GaAs (001) surface terminated with Ga or As atoms was performed by the molecular dynamics method using the analytical Bond-Order Potential based on quantum mechanical theory incorporating both σ- and π- bonds between atoms. A decrease in values of potential energy of the atoms during formation of isolated surface dimer have been determined. It has been found that potential energy of an atom in As-dimer is several tenths of an eV lower than in Ga-dimer. Kinetics of the initial stages of Ga-dimers formation in the temperature range of 25 - 40 K was studied. It was found that the characteristic thermal activation energy of single isolated Ga-dimers formation is ~ 29 meV, which is lower than the same value for As-dimers (~ 38 meV). Time constants characterizing the average rate of transformation of one dimer into a chain of two dimers at temperature range of 28 - 37 K were estimated. Inverse values of these parameters for paired Ga- and As-dimers are in the ranges of 10^11 – 10^12 s^-1 and 10^9 – 10^10 s^-1, respectively, while corresponding parameters for the formation of single dimers are in the ranges of 4·10^6 – 10^8 s^-1 and 1.4·10^6 – 7.4·10^7 s^-1.