arXiv subjects

Nayeli Zuniga-Hansen

Publications and source records attributed to Nayeli Zuniga-Hansen.

3 recordsLinked to original sources

arXiv2019

Effect of surface morphology on kinetic compensation effect

As part of a systematic study on the kinetic compensation effect, we use kinetic Monte Carlo simulations to observe the effects of substrate topology on the transient variations in the Arrhenius parameters - effective activation energy $E_{a}$, and preexponential factor $ν$ - during thermal desorption, with a particular focus on differences between ordered and disordered surfaces at a fixed global coordination number. The rates of desorption depend on surface configuration due to the inherent differences in the local environments of adsorbing sites in the two cases. While the compensation effect persists for the disordered substrate, the change in topology introduces an element that produces variations in $ν$ that are independent of variations in $E_{a}$, which implies that the parameters cannot be fully characterized as functions of each other. We expect our results to provide a deeper insight into the microscopic events that originate compensation effects in our system of study but also in other fields where these effects have been reported.

cond-mat.stat-mech↗

arXiv2017

Breakdown of Kinetic Compensation Effect in Physical Desorption

The kinetic compensation effect (KCE), observed in many fields of science, is the systematic variation in the apparent magnitudes of the Arrhenius parameters $E_a$, the energy of activation, and $ν$, the preexponential factor, as a response to perturbations. If, in a series of closely related activated processes, these parameters exhibit a strong linear correlation, it is expected that an isokinetic relation will occur, then the rates $k$ become the same at a common compensation temperature $T_c$. The reality of these two phenomena continues to be debated as they have not been explicitly demonstrated and their physical origins remain poorly understood. Using kinetic Monte Carlo simulations on a model interface, we explore how site and adsorbate interactions influence the Arrhenius parameters during a typical desorption process. We find that their transient variations result in a net partial compensation, due to the variations in the prefactor not being large enough to completely offset those in $E_a$, both in plots that exhibit a high degree of linearity and in curved non-Arrhenius plots. In addition, the observed isokinetic relation arises due to a transition to a non-interacting regime, and not due to compensation between $E_a$ and $\lnν$. We expect our results to provide a deeper insight into the microscopic events that originate compensation effects and isokinetic relations in our system, and in other fields where these effects have been reported.

cond-mat.stat-mech↗

arXiv2012

Effects of Noise, Correlations and errors in the preparation of initial states in Quantum Simulations

In principle a quantum system could be used to simulate another quantum system. The purpose of such a simulation would be to obtain information about problems which cannot be simulated with a classical computer due to the exponential increase of the Hilbert space with the size of the system and which cannot be measured or controlled in an actual experiment. The system will interact with the surrounding environment, with the other particles in the system and be implemented using imperfect controls making it subject to noise. It has been suggested that noise does not need to be controlled to the same extent as it must be for general quantum computing. However the effects of noise in quantum simulations and how to treat them are not completely understood. In this paper we study an existing quantum algorithm for the one-dimensional Fano-Anderson model to be simulated using a liquid-state NMR device. We calculate the evolution of different initial states in the original model, and then we add interacting spins to simulate a more realistic situation. We find that states which are entangled with their environment, and sometimes correlated but not necessarily entangled have an evolution which is described by maps which are not completely positive. We discuss the conditions for this to occur and also the implications.

quant-ph↗