In molecular dynamics (MD) simulations the need often arises to maintain such parameters as temperature or pressure rather than energy and volume, or to impose gradients for studying transport properties in nonequilibrium MD A method is described to realize coupling to an external bath with constant temperature or pressure with adjustable time constants for the coupling The method is easily extendable to other variables and to gradients, and can be applied also to polyatomic molecules involving internal constraints The influence of coupling time constants on dynamical variables is evaluated A leap‐frog algorithm is presented for the general case involving constraints with coupling to both a constant temperature and a constant pressure bath

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Molecular dynamics with coupling to an external bath.

A molecular dynamics simulation method which can generate configurations belonging to the canonical (T, V, N) ensemble or the constant temperature constant pressure (T, P, N) ensemble, is proposed. The physical system of interest consists of N particles (f degrees of freedom), to which an external, macroscopic variable and its conjugate momentum are added. This device allows the total energy of the physical system to fluctuate. The equilibrium distribution of the energy coincides with the canonical distribution both in momentum and in coordinate space. The method is tested for an atomic fluid (Ar) and works well.

A molecular dynamics method for simulations in the canonical ensemble

A stoichiometric derivative of graphene with a fluorine atom attached to each carbon is reported Raman, optical, structural, micromechanical, and transport studies show that the material is qualitatively different from the known graphene-based nonstoichiometric derivatives Fluorographene is a high-quality insulator (resistivity >10(12) Omega) with an optical gap of 3 eV It inherits the mechanical strength of graphene, exhibiting a Young's modulus of 100 N m(-1) and sustaining strains of 15% Fluorographene is inert and stable up to 400 degrees C even in air, similar to Teflon

/pdf/fluorographene-a-two-dimensional-counterpart-of-teflon-2eoe4l6d9z.pdf

Fluorographene: A Two‐Dimensional Counterpart of Teflon

As compared to bulk materials, magnetic nanoparticles possess distinct magnetic properties and attempts have been made to exploit their beneficial properties for technical and biomedical applications, e.g. for magnetic fluids, high-density magnetic recording, or biomedical diagnosis and therapy. Early magnetic fluids (MFs) were produced by grinding magnetite with heptane or long chain hydrocarbon and a grinding agent, e.g. oleic acid [152]. Later procedures for MFs precipitated Fe 3+/Fe 2+ of an aqueous solution with a base, coated the particles by oleic acid, and dispersed them in carrier liquid [161]. However, besides the elemental composition and crystal structure of the applied magnetic particles, particle size and particle size distribution determine the properties of the resulting MF. Many methods for nanoparticle synthesis including the preparation of metallic magnetic particles have been described in the literature. However, there still remain important questions, e.g. concerning control of particle size, shape, and monodispersity as well as their stability towards oxidation. Moreover, peptization by suitable surfactants or polymers into stable MFs is an important issue since each application in engineering or biomedicine needs special MFs with properties adjusted to the requirements of the system.

Synthesis and Characterization

https://cyberleninka.org/article/n/323323.pdf

Production and processing of graphene and 2d crystals

PURPOSE:To obtain a recording material excellent in the long-term dispersion stability of pigment and desirable for a writing utensil such as a ball-point pen or a sign pen by adding a surface-treated pigment with a fluorine gas to a recording material such as an ink. CONSTITUTION:The material contains a pigment surface-treated with a fluorine gas. It is prepared by mixing a fluorine-modified pigment with an untreated pigment, a solvent and a resin. The temperature of surface treatment is desirably -80 to 50 deg.C. The treatment time is usually about 0.5-60min. The pigment is not particularly limited, and an inorganic pigment and an inorganic pigment can be used.

Recording material coating fluorinated modified pigment

塩化マグネシウムの電解における陰極電流効率の低下に対する酸化マグネシウムおよび酸化ホウ素の作用機構について検討した。酸化マグネシウムはマグネシウムの溶解度には影響しないので,その効果は浴中へのマグネシウム粒子の分散を引き起こすためと考えられる。このようなマグネシウム粒子の凝集の妨害は, 溶融塩中に分散した酸化マグネシウムがマグネシウム粒子の表面に吸着することによるものと推定される。また, 酸化ホウ素の添加はマグネシウムの溶解度にほとんど影響がないうえ, これは陰極で電気化学的な還元もうけない。しかし, 酸化ホウ素はマグネシウムと反応してマグネシウムの損失をまねくばかりでなく, 反応の結果マグネシウム粒子の表面に酸化マグネシウムやホウ化マグネシウムなどを生成する。そのため, マグネシウム粒子の分散をも助長することになるので, マグネシウムの電流効率は大きく低下するものと推定される。

Influence of Magnesium Oxide and Boron Oxide on Metal Fog of Magnesium

A study was made of the electrochemical characteristics of graphite fluoride—lithium batteries in various non-aqueous solvents. Two types of graphite fluorides, (C 2 F) n and (CF) n were used as cathode materials. The discharge characteristics of graphite fluorides were better in dimethylsulfoxide, γ-butyrolactone, propylene carbonate and sulfolane in that order. The relation between electrode potential of graphite fluoride and solvation energy of lithium ion with each solvent indicates that solvated lithium ion is intercalated into traphite fluoride layers by the electrode reaction. Both the difference in the overpotentials and in the rates of OCV recovery among these solvents further supports the proposed reaction mechanism.

Solvents effects on electrochemical characteristics of graphite fluoride-lithium batteries

Ternary intercalation compounds, C x F(AlF 3 ) y and C x F(MgF 2 ) y containing active fluorine atoms adsorbed on carbon layers of host graphite were used as a cathode material of lithium cell. The discharge potentials are 2.8–2.5 V at current densities 40–400 μA cm −2 , being higher than that for graphite fluoride below 300 μA cm −2 . X-ray diffraction analysis and ESCA measurement of the discharge products indicate the formation of a new intercalation compound C x (LiF) ( M F n ) y , ( M = Al or Mg, n = 3 or 2).

Electrochemical behavior of graphite intercalation compounds of fluorine and metal fluorides

PURPOSE:To provide a three-component graphite interlaminar compound composed of graphite, AlF3 and F, stable to moisture, and having excellent electrical conductivity. CONSTITUTION:Natural graphite or artificial graphite obtained by the thermal treatment of petroleum coke, etc. is made to contact with AlF3 in fluorine atmosphere at 0-400 deg.C at least until the weight of the graphite beings to increase. After the completion of the reaction, the temperature of the reaction system is lowered to the room temperature, and the unreacted AlF3 is separated from the system to obtain the objective three-component graphite interlaminar compound of formula CxF(AlF3)y. There are 4 stages in the graphite interlaminar compound, and the periodic distance Ic of CxF(Al)y is 9.4-9.5Angstrom at the 1st stage, 12.8-12.9 Angstrom at the 2nd stage, 16.1-16.2Angstrom at the 3rd stage, and 19.5-19.6Angstrom at the 4th stage. The three-component graphite interlaminar compound has high heat resistance as well as the above-mentioned characteristics.

Nobuatsu Watanabe

Papers

Recording material coating fluorinated modified pigment

Influence of Magnesium Oxide and Boron Oxide on Metal Fog of Magnesium

Solvents effects on electrochemical characteristics of graphite fluoride-lithium batteries

Electrochemical behavior of graphite intercalation compounds of fluorine and metal fluorides

Interlaminar compound in graphite of aluminum fluoride and fluorine and its preparation