Crystalline Substances Research Articles

Mineralogical Crystallography

Crystallography remains, for mineralogy, one of the main sources of information on natural crystalline substances [...]

Aluminum Hydroxide Impurities Occlusions and Contamination Sources

This paper is reporting the data concerning impurities occlusion in the dried, milled and classified aluminum hydroxide, the sources of contamination and the ways to control the purity of classified aluminum hydroxide as raw material for special aluminas. Mainly, all the micronic size particles, floating in the super-saturated Bayer liquors, are potential sources of occluded impurities in the aluminum hydroxide particles. There are several mechanisms for embedding the impurities in crystalline substances. Of these, most probable ones in the Bayer alumina process are: a) occlusion of the spent liquor drops containing impurities inside the polycrystalline aluminum hydroxide congregates; b) hetero-nucleation of aluminum hydroxide on the surface of particles or colloids containing one or more impurities (the foreign particles are seized inside a crystals or inside of a crystalline multi-particulate association); c) incorporation of available ions or molecule reactive fragments in the poor crystalline structures of aluminum hydroxide after nucleation, during different growth stages of all already aggregated particles, under certain super-saturations. d) building up bridges between the scanty aggregated particles or filling the inside hollows of these aggregates with new quickly crystallized material, including the particulate impurities, mainly, during large fluctuations of the super-saturation. Using scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy EDS (Apollo SSD detector, EDAX), the contributions of each of these mechanisms can be investigated simply and assumed from the collected data. It was shown that well crystallized phases originating directly from bauxite (like the aluminum substituted goethite and substituted hematite, rutile or quartz), as well as the well as the crystallized new born phases during specific Bayer reactions (like cancrinite, are not promoting directly the impurities occlusion. Poor crystalline phases (like sodalite and katoite or other secondary phases and their micronic size fragments are really sustaining impurities occlusion through all the acknowledged mechanisms.

Synthesis of Modifiers in the System Cao-Sio<sub>2</sub>-H<sub>2</sub>O and their Influence on the Non-Autoclave Silicate Materials’ Properties Using Aluminosilicate Binder

Improving the hydration hardening building materials’ operational properties is possible due to the stable macro-, micro-and nanostructures’ creation by the cementing material crystalline aggregate directed modification, which can be achieved through the use of various additives acting as crystallization centers. In the course of the studies, the synthesized modifier effect nature represented by the system was revealed CaO-SiO2-H2O (CSH) on the properties of non-autoclave silicate materials using aluminosilicate binder of various compositions. It has been established that the use of an aluminosilicate binder together with the addition of a CSH modifier increases the presence of a crystalline phase at all stages of hardening, as well as intensifies the synthesis of low-basic calcium hydro silicates with a higher crystallization degree in the system CaO-SiO2(Al2O3)-H2O represented by lime and clay rocks. This contributes to the micro-reinforced crystalline framework formation of the neoplasms with increased strength. Due to this, the pore space decreases and the amount of synthesized crystalline substance increases, which helps to increase the water resistance of the samples in all compositions. The samples using an aluminosilicate binder and the addition of a CSH modifier achieve maximum strength with a CaO content of not more than 10 wt. % The optimal CSH modifier addition is up to 1.5 wt. %, with 7 wt. %, CaO content in a mixture increase in strength is up to 6%.

Synthesis and characterization of barbarin, a possible source of unexplained aminorex identifications in forensic science.

Aminorex is a US DEA Schedule 1 controlled substance occasionally detected in racing horses. A number of aminorex identifications in sport horses were thought to have been caused by exposure to plant sources of aminorex. Glucobarbarin, found in plants of the Brassicaceae family, has been suggested as a potential proximate chemical source by being metabolized in the plant or the horse to aminorex. In Brassicaceae, glucobarbarin is hydrolyzed by myrosinase to yield barbarin, which serves as an insect repellant and/or attractant and is structurally related to aminorex. The synthesis, purification, and characterization of barbarin is now reported for use as a reference standard in aminorex related research concerning equine urinary identifications of aminorex and also for possible use in equine administration experiments. Synthesis of barbarin was performed via ring closure between phenylethanolamine and carbon disulfide in tetrahydrofuran with the catalyst pyridine under reflux. The reaction yielded a white crystalline substance that was purified and chemically characterized as barbarin for use as a Certified Reference Standard or for studies related to equine aminorex identification.

The adulterated XANAX pill: a fatal intoxication with etizolam and caffeine

A 49-year old man was found dead at home next to a glass containing a dried, white, crystalline substance and near a bag containing pills with the imprint XANAX, the trade name of alprazolam. A comprehensive screening of material collected during the autopsy revealed the presence of etizolam and caffeine in lethal concentrations (0.77 μg/mL and 190 μg/mL) but no trace of alprazolam. Benzodiazepine analogue etizolam is rarely prescribed in Germany, and as a result there are not many reports about fatal cases. It has anxiolytic, hypnotic, sedative and muscle-relaxant properties and is used for the short-term treatment of anxiety and panic attacks. The purine alkaloid caffeine, conversely, is the most widely used central nervous system stimulant. The following report outlines potentially the first reported case of a lethal combination of the downer etizolam and the upper caffeine in medical literature.

A REVIEW FROM HISTORICAL TO CURRENT-CELASTRUS PANICULATUS

Celastrus paniculatus is commonly known as “Malkangani”, widely distributed in the Maldives, Australia, China, Cambodia, Malaysia, Taiwan, Nepal, Thailand as well as in the Pacific Islands and all over India mainly Maharashtra, Orissa and Andaman and Nicobar group of Islands on an altitude of 1800m. It climbs up to over 10m. The leaves are ovate or elliptic in shape with dentate margin. Seeds are ellipsoid or ovoid, yellowish-brown in color and grow inside the capsules. Celastrus paniculatus (Malkangni) is used in Ayurveda as a nervine tonic, tranquilizer and diuretic and in rheumatism, gout, leprosy and asthma. Different Parts of Celastrus paniculatus after extraction and fractionation give different active constituents such as sesquiterpene esters-malkanguinol, malkangunin, sesquiterpene alkaloids-celapanin, celapanigin, alkaloids-celastrine, paniculatine, fatty acids-oleic acid, palmittic acid, linoleic acid and stearic acid, crystalline substance tetracasanol and sterol. Different pharmacological activities are anti-rheumatic, anti-fungal, nootropic activity, antimalarial activity, anti spermatogenic effect, anti-anxiety and anti-atherosclerotic effect. In the present review, our target is to search, bring together and compile the data of Celastrus paniculatus, which have less side effects and very valuable for the treatment of rheumatism. Related information is procured from various scientific publications using online, seek out engines such as Google scholar, Pubmed and Science Direct. A total of 200 articles was reviewed out of which 55 articles are selected to review for the description of the plant, parts used, chemical constituents, traditional uses and for reported activities.

Exploiting Kinetic Solubility Differences for Low Level Detection of Crystallinity in Amorphous Drug Formulations

Background: Enabling formulations have been implemented by the pharmaceutical industry as an effective tool for keeping Active Pharmaceutical Ingredient (API) in an amorphous state. Upon dosing in the amorphous state, many drugs which fail to demonstrate bioactivity due to the limited solubility and bioavailability of their crystalline form become bioavailable. Purpose: The analytical techniques use today for crystallinity detection are challenged by the sensitivity and robustness needed to achieve a 5% quantitation limit in low dose drug products. Our laboratory has developed a novel procedure capable of meeting this sensitivity and selectivity requirement. This is achieved by exploiting the differences in kinetic solubility of the formulated amorphous and free crystalline forms of API currently being used in dosage form platforms. Methods: Representative amorphous drug formulations were prepared and spiked with varying levels of crystalline drug substances to evaluate the selectivity and recovery of the crystalline drug substance from the product formulation. Kinetic solubility testing using a (i) Particle wetting phase, (ii) Particle suspending/erosion phase, (iii) Sampling time point and (iv) A total recovery determination for the drug substance. Results: The method selectively and quantitatively distinguishes crystalline drug substance from amorphous drug substance for samples spiked from 2.5% to 10% of the nominal label concentration of the API in the dosage form matrix. Conclusion: The kinetic solubility approach reported here achieves sensitive crystallinity quantitation for low drug level amorphous drug formulations at levels not yet achieved by complimentary analytical techniques.

Synthesis of Ordered Carbonaceous Framework with Microporosity from Porphyrin with Ethynyl Groups

One of the challenging targets in materials synthesis is a direct conversion of molecular based crystalline substances into crystalline ordered carbonaceous frameworks (OCFs). Though we have discov...

Spherulitic microbialites from modern hypersaline lakes, Rottnest Island, Western Australia.

Fibrous-radiating carbonate spherulites spatially associated with poorly crystalline Mg-Si substances have formed within conical microbialites in modern hypersaline lakes on Rottnest Island, Western Australia. Two spherulitic fabrics can be distinguished based on compositional and textural differences. The oldest (lowermost) fabric comprises variably intergrown aragonitic spherulites 100-500μm wide, containing micritic nuclei with coccoid cell molds in various stages of cell division. Spherulite matrices contain aggregates of individual nanospheres 150-200nm wide, composed of a poorly crystalline Mg-Si phase, locally containing cell molds with similar dimensions to those within spherulite nuclei. The younger (upper) fabric comprises sub-polyhedral networks of mineralized EPS composed of an Mg-Si substance. The polyhedrons contain aragonite-replaced coccoid cells, voids, and polyhedral spherulites 8-12μm wide with a morphology determined by fossil EPS, interpreted to have been produced by coccoid cyanobacteria. These spherulites are composed of high-Mg calcite, inferred to have formed in association with heterotrophic bacteria. Stable isotope data, textural relationships, and geochemical modeling are consistent with cyanobacterial oxygenic photosynthesis influencing the precipitation of Mg-Si substances and aragonitic spherulites by locally increasing the pH. The morphology of the polyhedral spherulites suggests the former presence of EPS and that faceted spherulites with similar dimensions in the geological record may represent biosignatures. The Rottnest Island conical microbialites demonstrate an intimate association between microbial features and processes and spherulitic fabrics, potentially providing insights into texturally and compositionally similar features in the geological record.

Study on the inorganic synthesis from recycled cement and solid waste gypsum system: Application in grouting materials

Grouting reinforcement technology plays an important role in the field of disaster prevention and control of deep underground engineering. Due to the insufficient workability and mechanical property of recycled cement (RC) under high water to solid ratio, there is still a blank about recycled cement used in grouting materials. In order to propose a new high-performance, low-cost environmental grouting materials and expand the application field of RC, this study examined the effect of phosphogypsum and flue gas desulfurization gypsum on the performance and microstructure of RC thermal activated with different temperatures, high purity natural gypsum and blank sample were designed as control group. Test results indicated that three kinds of gypsum all prolonged the initial setting times, and improved the fluidity and mechanical properties of RC grouts. Especially, 10% phosphogypsum added to the 750 °C thermal activated RC, optimal proportion of RC to gypsum system, can obtain a higher compressive strength (6.33 MPa for 3d and 11.26 MPa for 28d) than P.O.42.5 cement with 1.0 water to solid ratio, prolong the initial setting times from 5 min up to 27 min, which makes the RC capable of using as grouting materials. The microscopicanalysis results showed that the increase in the compressive strength was attributed to gypsums can promote the generation process of C-S-H and ettringite in RC, the impurity of phosphogypsum also participate in the hydration process and generated crystalline substances such as calcium phosphate silicate.

AnSen (An = Th, U, Np, Pu, Am, or Cm) Coordination Polyhedra in Crystal Structures

Voronoi–Dirichlet (VD) polyhedra have been used to make a crystal-chemical analysis of compounds containing in their crystal structure coordination polyhedra AnSen (An = Th, U, Np, Pu, Am, or Cm). It was found that atoms An(II), An(III), An(IV), and An(V) occur in selenides. These atoms coordinate from 6 to 10 selenium atoms in the form of Se2– or Se–. It was shown that the VD polyhedra make it possible to determine the valence state of An atoms in structures of crystalline substances and reveal errors in the crystal-structural information. A dependence of the multiplicity of Se–Se bonds on their length in 0D, 1D, and 2D groups composed of only selenium atoms was determined.

Comparison of Some Molecular Structures by Minimizing the Comparison Function

The geometric difference in the relative arrangement of atoms in molecules with the same chemical formula significantly affects the properties of the crystal. For quantitative comparison of the spatial geometric structure of two molecules, we used the method of optimal superposition of molecules through the minimization of a certain comparison function by rotating the molecules after superposing their centers of mass. The search for the minimum of the comparison function over Euler rotation angles is performed by the Rosenbrock method. The assumed criterion for comparing molecules allows us to quantify the proximity in the spatial structure of molecules. The implementation of the method is shown by comparing the structure of eight molecules in four crystalline substances.

Тест-метод определения фосфат-ионов в органической продукции и почве с применением блистерных ячеек

A test method for the determination of phosphates in environmental objects has been developed, the determination of phosphate ions can be carried out in the field, the analysis of one sample is carried out for 10-15 minutes. Color characteristics can be monitored both visually and using color processing programs for smartphones such as ON Color Measure or Light Analyzer. Variants of compositions of a series of placers are proposed for visually blister colorimetric determination of phosphate ion concentrations in a blister cell (tablet for tablets) containing a mixture of reagents. The placers allow the quantitative determination of phosphates in various objects without preliminary preparation of reagent solutions. The application of reagents to the surface of silica gel makes it possible to isolate all reagents until a chemical reaction occurs. Each component in a separate placer is isolated, stable for 6 months. Test systems are recommended for semi-quantitative visual testing and for the quantitative determination of the content of phosphate ions in solutions. The composition and application conditions of crystalline substances - reagents capable of providing a sufficiently high acidity with the addition of a few drops of a solution and a reducing agent suitable under blister conditions have been optimized. Visual-colorimetric reaction is carried out under conditions when the volume of the added solution is 2-3 drops. In the environmental objects of the Belogorsky district of the Republic of Crimea, the concentrations of phosphate ions in water samples, soil of carbonate chernozem, biomass of cellulose-containing waste of lavender after extraction of lavender essential oil grown by organic farming were determined. The phosphate content was estimated by the visual blister method in the samples and standard methods, and good convergence of the analysis results was shown.

Response Surface Methodology for Optimization of Process Variables of Atorvastatin Suspension Preparation by Microprecipitation Method Using Desirability Function

Background : Atorvastatin (AT), as a synthetic lipid-lowering agent, is a highly crystalline substance having poor solubility and low bioavailability. The objective of the present research was to improve the microprecipitation method of AT suspension preparation. Methods: Microprecipitation parameters were improved using Box-Behnken experimental design method. The suspension was formulated with Brij 35 (stabilizer agent) using methanol as solvent and water as non-solvent, respectively. DSC, XRD, FTIR studies were performed for characterization of the microcrystals. With the aim of evaluating the effect of independent variables, the amounts of organic solvent (X1), emulsifier concentration (X2), stirring rate (X3), and volume of aqueous solvent (X4) on dependent variables, drug content (DC,) particle size (PS), drug released after 5 minutes (Q5), Gibbs free energy change (ΔG°tr), crystal yield (CY) and saturated solubility (Ss), a full factorial was used. Results: The results of DSC, XRD, and FTIR showed that there was not any interaction between AT and Brij 35. This research demonstrated a reduction in crystallinity in agglomerates. The microcrystals showed that micromeritics characteristics were significantly improved compared to pure AT. The content of drug and yield crystal was in the limit of 42.58-110.24% and 58.33-98.18% in all formulations, respectively. It was shown that the prepared microcrystals had a higher rate of release compared to the untreated AT powder (P< 0.05). Size reduction of AT is needed for improving the solubility. Solubility and drug release rates of At was enhanced with the microprecipitation method. Conclusion: The results showed that microcrystals significantly increased AT dissolution rate.

SYNTHESIS AND STRUCTURE OF METHYLTRIPHENYLPHOSPHONIUM DICYANODIBROMOAURATE [Ph3PCH3] [Au(CN)2Br2

Methyltriphenylphosphonium dicyanodibromoaurate (1) [Ph3PMe]+[Au(CN)2Br2]– was synthesized by the reaction of potassium dicyanodibromoaurate with methyltriphenylphosphonium bromide in an aqueous solution and was structurally characterized. The complex is a yellow-colored, air-resistant crystalline substance with a clear melting point. The structure of the compound was established by IR spectroscopy, NMR spectroscopy and X-ray diffraction analysis. An intense absorption band was observed in the IR spectrum of compound at 2220 cm−1, corresponding to the stretching vibrations of cyano groups. The absorption band of the deformation vibrations of the P – СPh bonds in the IR spectrum is at 1438 cm−1. In the recorded 1Н, 13С, and 31Р NMR spectra, signals are observed for the number, value of chemical shifts and integral intensity that do not contradict the proposed complex structure. The X-ray diffraction analysis of crystal 1 was carried out on a Bruker D8 QUEST diffractometer (MoKα radiation, λ = 0.71073 Å, graphite monochromator). [C21H18AuBr2N2P, M = 686.13, crystal system triclinic, space group P-1, a = 8.802(5), b = 8.989(5), c = 15.233(11) Å, V = 1143.8(13) Å3, Z = 2, µ = 10.002 mm-1, F(000) = 644, crystal size 0.41×0.30×0.22 mm]. According to the X-ray diffraction analysis (XRDA) data there are two types of centrosymmetric crystallographically independent monomeric dicyanodibromoaurate anions and methyltriphenylphosphonium cations in the crystal of compound MFDDA. The cations have a distorted tetrahedral configuration: the CPC angles equal 108.8(2)°−110.0(2)°, the P−С distances are 1.791(5)−1.800(5) Å. All СAuC and BrAuBr trans-angles are 180.0° in the [Au(CN)2Br2]− anions. The Au−C distances in anions differ from each other and equal 2.040(7), 2.024(1), 1.991(2) Å. These values are close to the sum of the covalent radii of atoms (2.03 Å). The Au-Br bond lengths are equal to 2.4162(14), 2.4591, 2.474(5) Å in dicyanodibromoaurate anions. Formation of the crystal structure occurs due to formation of weak N···Н−С hydrogen bonds between cations and anions (2.68, 2.59, 2.38 Å) and Br···Н−С (3.03, 3.02 Å). Complete tables of coordinates of atoms, bond lengths and valence angles are deposited at the Cambridge Crystallographic Data Centre.

Antimicrobial and Phytochemical Screening of the Methanolic Stem Bark Extract of Ficus abutilifolia (Miq.) and Some Spectral Studies on One Isolated Component

The stem bark extract of Ficus abutilifolia (Miq.) , an ethnomedicinally important member of the Moraceae family, was analysed with the three-fold aim of identifying its phytochemical components, determining its antimicrobial effects and efficacy, and isolating a component to be structurally elucidated by Fourier-Transform Infrared (FTIR) and Proton Nuclear Magnetic Resonance ( 1 HNMR) studies. Extraction was carried out by maceration method with methanol as the extraction solvent. Qualitative phytochemical analysis of the resulting methanolic extract gave positive results for carbohydrates, cardiac glycosides, saponins, steroid, triterpenes and alkaloids, while the antimicrobial screening revealed bioactivity against Staphylococcus aureus , Escherichia coli , and Pseudomonas aeruginosa . The extract was found to be bacteriostatic (growth-inhibitory) to S. aureus , E. coli and P. aeruginosa with respective Minimum Inhibitory Concentration (MIC) values of 25-, 50- and 25 mg/ml, but was bactericidal (lethal) only to S. aureus and P. aeruginosa with a common Minimum Bactericidal Concentration (MBC) value of 50 mg/ml. Column separation led to the successful isolation of a white crystalline substance with R f value of 0.25 using solvent ratio 1:4 of EtOAc:n-hexane solvent system. Studies on the FTIR and 1 HNMR spectra of the isolated compound revealed that it is a non-aromatic, non-conjugated six-membered lactone. Keywords: Ficus abutilifolia , antimicrobial screening, phytochemical, structural elucidation, isolation, stem bark, chromatography DOI: 10.7176/JNSR/10-6-05 Publication date: March 31 st 2020

Mathematical modeling of perspective structures of metal oxides

Information about the structure and properties of materials is especially important when working with micro-and nanoscale objects due to the high complexity of their obtaining. This makes it relevant to use computer modeling to predict the required characteristics of materials. Electronic, magnetic, mechanical, and other properties of crystalline substances are determined by their structure-the periodicity of the lattice and the symmetry of the unit cell. This article discusses metal oxides with the general chemical formulas MeO (metals: Ca, Cd, Mg), MeO2 (metals: Hf, Ce, Zr), Me2O3 (metals: Er, Nd, Sc, Mn, Tl) and Me3O4 (using Fe as an example) and a cubic symmetry type crystal lattice — structural types NaCl (rock salt), Fluorite, Bixbyite, Spinel accordingly. The paper describes the model of ion-atomic radii, which is widely used in the modeling of crystalline metal oxides. The application of the annealing simulation algorithm for calculating the metric parameters of the compounds under consideration is shown. The software implementation of the algorithm presented in this paper allows us to determine the coordinates of the atoms that are included in the elementary cell of the crystal lattice, calculate the lattice constant and the density of the packing of atoms in the crystal cell using the specified chemical formula and the space group symmetry. These structural characteristics can be used as input parameters for determining electronic, magnetic, and other properties. The article compares the values of lattice constants obtained as a result of modeling with experimental data.

SYNTHESIS OF NEW BROMINE ACETYLENE DITHIOCARBAMATES DERIVATIVES AND THEIR GROWTH-STIMULATING ACTIVITY.

The proposed article relates to organic chemical synthesis and the study of new bromo-acetylene dithiocarbamates, the chemical properties of 1-isothiocyanate and 1-thiolacetylene esters of bromo-substituted benzoic acid, which are crystalline substances that are readily soluble in many organic solvents and insoluble in water. The structure of the bromine derivatives of acetylene dithiocarbamates was established by elemental analysis, IR and PMR spectroscopy. A probable mechanism of the interaction of 1-thiolpropargyl ethers with 1-isothioisocyanatepropargyl ethers is presented.With an increase in the nucleophilicity of the groups, the rates of addition and the yields of the final products increase, with a decrease in basicity and an increase in steric factors of the radicals, the rates of yield of the reaction products decrease slightly. Comparative tests show that the test derivative of the drug 1 - [(ortho-bromobenzoate-propynyl) -11- (ortho-bromobenzoate-propynyl) dithiocarbamate] showed a higher growth-promoting activity.

Health Benefits of Quassin from Quassia amara: A Comprehensive Review of their Ethnopharmacological Importance, Pharmacology, Phytochemistry and Analytical Aspects

: Medicinal plants have been indispensable to human life as they are used in food, cosmetics, medicines, nutraceuticals, perfumery, beverages and many more sectors. The medicinal plant contains various important classes of phytochemicals and broadly they are categorized into either primary or secondary metabolite. A large number of modern medicines are mainly derived from plant and other natural sources. Medicinal properties of plants are mainly due to the presence of their secondary metabolite and good examples are salicylic acid, morphine, quinine, vincristin and vinblastine. In spite of the great discovery of allopathic medicine, plant pure phytoconstituents play an important role in the modern medicine. Various plant based medicine are available in the market and people are using it on the basis of the belief that it is safer compared to the allopathic medicine. Furthermore, based on these believes, people use most of the traditional medicines in their routine life for the treatment of numerous disorders and this is called self-medication. Quassia amara plant belongs to Simaroubaceae family which is one of the best examples of the self-medicated plant. Traditionally Quassia amara has antimalarial, stomachic, antianaemic, antibiotics, cytotoxic and antiamoebic activity. Its reproductive, insecticidal, larvicidal and vermifuge properties have been also reported in the literature. Quassinoids are the important phytoconstituents of this plant and are the main bitter principles of Quassia amara too. Quassin is a white crystalline substance and is widely used in Chinese herbal medicine for their bitter taste. The purpose of this review is to gain an understanding of the Quassin and Quassia amara and to present information and knowledge regarding this phytoconstituent. Medicinal uses, pharmacological importance and various bioanalytical methods of Quassin and Quassia amara have been presented in this review. The benefit of this review is to get better understanding and ideas of Quassin and Quassia amara research findings in various disciplines. Furthermore, there is a need to perform more scientific investigation to explore the other beneficial properties of Quassia amara and Quassin.

Thermal decomposition and diffusion of methane in clathrate hydrates from quantum mechanics simulations.

Clathrate hydrates are ice-like crystalline substances in which small gas molecules are trapped inside the polyhedral cavities of water molecules. They are of great importance in both scientific research and the petroleum industry because of their applications in modern energy and environmental technologies. To achieve an atomistic-level understanding of the diffusion and decomposition of trapped molecules in clathrate hydrate, we used methane hydrates (MHs) as the prototype system and examined the methane diffusion and decomposition mechanism by employing quantum mechanics (QM) and quantum mechanics molecular dynamics (QMD) simulations. Our QMD simulations illustrated that the initial decomposition reaction in MHs initiates from hydrogen transfer among water molecules and attacks by fragments of O and OH on CH4 molecules are responsible for the destruction of the methane molecules. Next, our QM simulations revealed that the methane molecule prefers to escape from the ice cage through the hexagonal face at low temperature. To suppress the methane diffusion, we demonstrated that the diffusion barrier is significantly enhanced by adding electron or hole carriers. This is because the extra electrons and holes enhance the electrostatic interaction between methane and water molecules, leading to an increased diffusion barrier. Thus, the clathrate hydrates could be stabilized by adding extra free electron or hole carriers.