Thermodynamics and Phase Transition of Topological Dilatonic Lifshitz-Like Black Holes

It is known that scalar-tensor gravity models can be studied in Einstein and Jordan frames. In this paper, a model of scalar-tensor gravity in Einstein's frame is considered to calculate the Lifshitz-like black hole solutions with different horizon topologies. Thermodynamic properties and first order van der Waals-like phase transition are studied, and it is found that the Lifshitz parameter affects the phase structure. In addition, thermal stability is investigated by using the behavior of heat capacity and various methods of geometrical thermodynamics.     

DFT/TDDFT Investigation of Electronic,Magnetic, and Optical Properties of Graphene Containing Different Values of Se Impurity

Physics of the Solid State - The electronic, magnetic, and optical properties of graphene (gr) containing selenium impurities of 2, 3, 5.5, and 12.5% were calculated by DFT. By increasing the...     

The role of delay times in subcycle-resolved probe retardation measurements

The delay in the nonlinear response of matter to intense laser pulses has been studied since a long time regarding its nuclear contribution. In contrast, the electronic part of the nonlinear response in wide-band-gap dielectrics, which is usually dominant, is not well explored regarding its delay, and previous studies have revealed that the timescale is below 1 fs. Here, the influence of delay times on the recently introduced method of subcycle-resolved probe retardation measurements is investigated using a simulation. In the model assumed, the electronic nonlinearity is divided into the third order Kerr effect and the plasma contribution due to conduction band population in the strong laser field. In the regime of close-to-collinear pump-probe geometries, the probe retardation shows both π- and 2π-oscillations in the pump-probe delay. Sub-femtosecond delay times influence the phase of the oscillations significantly, but it remains difficult to distinguish the influence of the Kerr response from the plasma contribution.     

Ring Opening of Epoxides with Sodium Cyanide Catalyzed with Ce(OTf)4

Efficient and regioselective conversion of epoxides to β-hydroxy nitriles with sodium cyanide in the presence of catalytic amounts of Ce(OTf)₄ is described under solvent free conditions.     

Highly Regio- and Stereoselective Synthesis of β-Halohydrins from Epoxides Catalyzed with Ceric Ammonium Nitrate

Ce(IV) as ceric ammonium nitrate can effectively catalyze ring opening of epoxides with halides under very mild conditions and easy procedure to give the corresponding β-chloro-and β-bromohydrins in excellent yields. The reactions occur with both substituted and unsubstituted quaternary ammonium halides and with high regio- and stereoselectivity. The reaction of optically active styrene oxide with chloride ion was found to be highly stereospecific and afforded the corresponding β-halohydrin in 96% ee.     

Density functional studies of influences of Ni triad metals and solvents on oxidative addition of MeI to [M(CH3)2(NH3)2] complexes and C-C reductive elimination from [M(CH3)3(NH3)2I] complexes

Three metal square planar complexes of the type [M(CH₃)₂(NH₃)₂] (M = Ni, Pd, Pt), with a systematic variation in the metals, are chosen to investigating their S_N2-type oxidative addition reactions with methyl iodide by using the B3LYP levels of theory. The oxidative addition was found to take place via a transition state with a nearly linear arrangement of the I-CH₃-M moiety. Solvation effects in these oxidative addition reactions were also investigated. Considering the nature of the metal centre and solvation effects, the following conclusions emerge: (i) addition of MeI is exothermic for all three metals, and Pt is predicted to react with a much lower barrier than either Pd or Ni. The results describe that the MeI addition would be expected to be more favourable with the complex bearing the third-row metal (platinum) as compared to the other triad metals, nickel or palladium, in which case a more strongly bound MeI adduct is formed with a lower activation barriers and the reaction being more exothermic; (ii) the reaction is very difficult to occur in low polar solvents, such as benzene, due to the high barrier which is induced by dissociation of iodide anion from methyl group, but the reaction easily occurs in polar solvents, such as acetonitrile; this is attributed to the ability of polar solvents to solvate and therefore stabilize the related polar intermediate ion pair. Ethane reductive elimination from the M(VI) complexes fac-[M(CH₃)₃(NH₃)₂I] were also studied, indicating that the Ni(IV) and Pd(IV) complexes are very prone to undergo the reductive elimination while the Pt(IV) analogous is less reactive towards the reductive elimination. The results indicate that in contrast to the Me-Me reductive elimination, the S_N2 oxidative addition reaction of MeI to M(II) is much less sensitive to the nature of the metal centre, suggesting that the nucleophilicity of M(II) in [M(CH₃)₂(NH₃)₂] does not change significantly as one moves from M = Ni to Pt.