Movement behavior of residual oil droplets and CO2: insights from molecular dynamics simulations

After primary and secondary recovery of tight reservoirs, it becomes increasingly challenging to recover the remaining oil. Therefore, improving the recovery of the remaining oil is of great importance. Herein, molecular dynamics simulation (MD) of residual oil droplet movement behavior under CO2 displacement was conducted in a silica nanopores model. In this research, the movement behavior of CO2 in contact with residual oil droplets under different temperatures was analyzed, and the distribution of molecules number of CO2 and residual oil droplets was investigated. Then, the changes in pressure, kinetic energy, potential energy, van der Waals' force, Coulomb energy, long-range Coulomb potential, bond energy, and angular energy with time in the system after the contact between CO2 and residual oil droplets were studied. At last, the g(r) distribution of CO2–CO2, CO2-oil molecules, and oil molecules-oil molecules at different temperatures was deliberated. According to the results, the diffusion of CO2 can destroy residual oil droplets formed by the n-nonane and simultaneously peel off the n-nonane molecules that attach to SiO2 and graphene nanosheets (GN). The cutoff radius r of the CO2–CO2 is approximately 0.255 nm and that of the C–CO2 is 0.285 nm. The atomic force between CO2 and CO2 is relatively stronger. There is little effect caused by changing temperature on the radius where the maximum peak occurs in the radial distribution function (RDF)-g(r) of CO2–CO2 and C–CO2. The maximum peak of g(r) distribution of the CO2–CO2 in the system declines first and then rises with increasing temperature, while that of g(r) distribution of C–CO2 changes in the opposite way. At different temperatures, after the peak of g(r), its curve decreases with the increase in radius. The coordination number around C9H20 decreases, and the distribution of C9H20 becomes loose.

Influence of LDA+U on band dispersion in monolayer MCl2 (M: Fe, Co)

We investigated the effect of LDA+U on the band dispersions in 1T monolayer FeCl2 and CoCl2 within the self-consistent noncollinear calculation. As shown in the band dispersed, FeCl2 is metallic while CoCl2 is insulating. When the effective Coulomb energy takes into account, FeCl2 is metallic without band gap while the band gap in CoCl2 increases as the Coulomb energy increases. Thus, the band gap in CoCl2 can be effectively controlled by the Coulomb energy, thus it is feasible for spontaneous development.

Correlation of the Madelung constant and I—M—I bonding angle with cohesive energy contributions in layered metal diiodides (MI2) with CdI2 (2H polytype) structure

This study uses theoretically methods to investigate, for metal diiodides MI2 (M = Mg, Ca, Mn, Fe, Cd, Pb) with CdI2 (2H polytype) structure, the mutual correlation between the structure-characterizing parameters (the flatness parameter of monolayers f, the Madelung constant A, and bonding angle I—M—I) and correlation of these parameters with contributions of the Coulomb and covalent energies to cohesive energy. The energy contributions to cohesive energy are determined with the use of empirical atomic potentials. It is demonstrated that the parameters f and A, and the bonding angle I—M—I are strictly correlated and increase in the same order: FeI2 < PbI2 < MnI2 < CdI2 < MgI2 < CaI2. It is found that with an increase of parameter A and bonding angle I—M—I the relative contribution of the Coulomb energy to cohesive energy increases, whereas the relative contribution of the covalent energy decreases. For a hypothetical MX 2 layered compound with the CdI2 (2H polytype) structure, composed of regular MX 6 octahedra (angle X—M—X = 90°), the flatness parameter and the Madelung constant are found to be f reg = 2.449 and A reg = 2.183, respectively. Correlation of the covalent energy with the type of distortion of MI6 octahedra (elongation or compression) with respect to regular configuration (angle I—M—I = 90°) is also analyzed.

Period Doubling Phenomenon as the Origin of Electron Properties

It is proposed that the electrons have an intrinsic periodic property, which determines particle&rsquo;s rest energy, electric charge, and magnetic moment. Numerical analysis shows that the correct periods are generated by a precise period doubling cascade starting at the Planck scale. Periods corresponding to the values of the intrinsic physical properties of the electron and positron belong to a subset of stable periods. The periodic structures of the rest energy and magnetic moment consist of three internal degrees of freedom, whereas the Coulomb energy of the electric charge consists of four. The number of period doublings for the elementary charge determines the value of the fine structure constant alpha.

Connecting the SYK Dots

We study a putative (strange) metal-to-insulator transition in a granular array of the Sachdev–Ye–Kitaev (SYK) quantum dots, each occupied by a large number N ≫ 1 of charge-carrying fermions. Extending the previous studies, we complement the SYK couplings by the physically relevant Coulomb interactions and focus on the effects of charge fluctuations, evaluating the conductivity and density of states. The latter were found to demonstrate marked changes of behavior when the effective inter-site tunneling became comparable to the renormalized Coulomb energy, thereby signifying the transition in question.

On the origin of non-monotonic variation of the lattice parameters of LiNi1/3Co1/3Mn1/3O2 with lithiation/delithiation: a first-principles study

The non-monotonic variation of the lattice parameters of LixNi1/3Co1/3Mn1/3O2 during delithiation/lithiation is simulated and explained by using an approach combining an extensive set of Coulomb energy and DFT calculations.

Quasibound states of the Dirac field in Schwarzschild and Reissner–Nordström black hole backgrounds

In this paper, we study the existence of (quasi)bound states in two spacetime geometries describing Schwarzschild and Reissner–Nordström black holes. For obtaining these types of states, we search for discrete quantum modes of the massive Dirac equation in the two geometries. After imposing the quantization condition, an analytical expression for the energy of the ground states is derived. The energy of higher states is then obtained numerically. For very small values of the black hole mass M, we compare the energy of the Reissner–Nordström black hole quasibound state with the Dirac–Coulomb energy and we have found the two to be in good agreement.