Search results for "functional"
showing 10 items of 4822 documents
Instability of the topological surface state in Bi2Se3 upon deposition of gold
2017
Momentum-resolved photoemission spectroscopy indicates the instability of the Dirac surface state upon deposition of gold on the (0001) surface of the topological insulator Bi2Se3. Based on the str ...
Rashba splitting of the Tamm surface state on Re(0001) observed by spin-resolved photoemission and scanning tunneling spectroscopy
2020
Physical review research 2(1), 013296 (2020). doi:10.1103/PhysRevResearch.2.013296
Calculations of atomic and electronic structure for (100) surfaces of SrTiO3 perovskite
2002
AbstractWe present and discuss main results of the calculations for the surface relaxation and rumpling of SrTiO3 surfaces with TiO2 and SrO terminations using a wide variety of methods of modern computational physics and chemistry, including the shell model (SM) and ab initio methods based on Hartree-Fock (HF) and Density Functional Theory (DFT). The HF and DFT formalisms with different exchange-correlation functionals are implemented into Crystal-98 computer code using a Gaussian-type basis set. We demonstrate that a hybrid B3PW formalism gives the best results for the bulk SrTiO3 properties. Results are compared with previous ab initio plane-wave LDA calculations and LEED experiments. Ou…
Constraining the surface properties of effective Skyrme interactions
2016
The purpose of this study is threefold: first, to identify a scheme for the determination of the surface energy coefficient a_surf that offers the best compromise between robustness, precision, and numerical efficiency; second, to analyze the correlation between values for a_surf and the characteristic energies of the fission barrier of Pu240; and third, to lay out a procedure how the deformation properties of the Skyrme energy density functional (EDF) can be constrained during the parameter fit. There are several frequently used possibilities to define and calculate the surface energy coefficient a_surf of effective interactions. The most direct access is provided by the model system of se…
Symmetry of minimizers with a level surface parallel to the boundary
2015
We consider the functional $$I_\Omega(v) = \int_\Omega [f(|Dv|) - v] dx,$$ where $\Omega$ is a bounded domain and $f$ is a convex function. Under general assumptions on $f$, G. Crasta [Cr1] has shown that if $I_\Omega$ admits a minimizer in $W_0^{1,1}(\Omega)$ depending only on the distance from the boundary of $\Omega$, then $\Omega$ must be a ball. With some restrictions on $f$, we prove that spherical symmetry can be obtained only by assuming that the minimizer has one level surface parallel to the boundary (i.e. it has only a level surface in common with the distance). We then discuss how these results extend to more general settings, in particular to functionals that are not differenti…
On the significance of molecular surfaces and thermodynamic interactions for the excess viscosities of liquid mixtures
1994
The viscosities η of homogeneous binary mixtures of liquids are usually approximated as In η = ϕ1 In η1 + ϕ2 In η2 where ϕi and ηi are the volume fractions and the viscosities, resp., of the i-th pure substance; the behavior of real systems is then discussed in terms of Δ In η, the deviations from the above reference behavior. Here a semi-empirical approach is presented according to which volume fractions are replaced by the surface fractions Ωi to create a more realistic reference state, and the thermodynamic interaction parameter g is taken into account. The new equation reads (expressing it for practical purposes still in the terms of ϕi) γ is a geometric factor, measuring the difference…
Molecular surface calculations on organic compounds
1992
Abstract The molecular surface area was calculated for 82 hydrocarbons, esters, ethers, alcohols and ketones including linear, branched and cyclic ones. The relationship between the aqueous solubility and the molecular surface area was determined for each family of compounds and for all the families together. The results show that solubility is mainly determined by molecular surface area and that the influence of functional group is the same for all the oxygen containing compounds studied.
Quantifying the limits of transition state theory in enzymatic catalysis
2017
Significance Transition state theory (TST) is the most popular theory to calculate the rates of enzymatic reactions. However, in some cases TST could fail due to the violation of the nonrecrossing hypothesis at the transition state. In the present work we show that even for one of the most controversial enzymatic reactions—the hydride transfer catalyzed by dihydrofolate reductase—the error associated to TST represents only a minor correction to the reaction rate. Moreover, this error is actually larger for the reaction in solution than in the enzymatic active site. Based on this finding and on previous studies we propose an “enzymatic shielding” hypothesis which encompasses various aspects …
Effect of H Adsorption on the Magnetic Properties of an Fe Island on a W(110) Surface
2019
<p>Low-dimensional materials, such as ultrathin films, nanoislands and wires, are actively being researched due to their interesting magnetic properties and possible technological applications for example in high density data storage. Results of calculations of an Fe nanoisland on a W(110) support are presented here with particular focus on the effect of hydrogen adsorption on its magnetic properties. This is an important consideration since hydrogen is present even under ultra-high vacuum conditions. The calculations are based on density functional theory within the generalized gradient approximation. The adsorption of H atoms is found to strongly decrease the magnetic moment of the …
Reply to "comment on 'Monte Carlo simulations for a Lotka-type model with reactant surface diffusion and interactions' ".
2002
As is well known, a wide class of physical problems, including the kinetics of heterogeneous catalytic reactions, is traditionally described in terms of the master equations ~ME!. The definition of ME allows us not only to perform Monte Carlo ~MC! simulations, but also to develop at the same time appropriate analytical methods @mean field~MF!, cluster approximations, etc. #@ 1#. ME is formally defined when all possible states of a system and the transition rates between these states are specified. This is enough to define only the transition rates K(i! j ) for such elementary processes as particle adsorption, desorption, diffusion, reaction, etc., from the initial state i to the final state…