On the calculation of time correlation functions by potential scaling

We present and analyze a general method to calculate time correlation functions from molecular dynamics on scaled potentials for complex systems for which simulation is affected by broken ergodicity. Depending on the value of the scaling factor, correlations can be calculated for times that can be orders of magnitude longer than those accessible to direct simulations. We show that the exact value of the time correlation functions of the original system (i.e., with unscaled potential) can be obtained, in principle, using an action-reweighting scheme based on a stochastic path-integral formalism. Two tests (involving a bistable potential model and a dipeptide bond-vector orientational relaxation) are exemplified to showcase the strengths, as well as the limitations of the approach, and a procedure for the estimation of the time-dependent standard deviation error is outlined.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87881/2/034110_1.pd

Molecular modeling in confined polymer and biomembrane systems

The computational study of soft materials under confinement for bio- and nanotechnology still poses significantchallenges but has come a long way in the last decade. It is possible to realistically model and understand the fundamentalmechanisms which are at play if soft materials are confined to nanometer dimensions. Here, we present several recentexamples of such studies. Thin polymer films are abundantly used as friction modifiers or steric stabilizers. We show howsystematic modeling can shed light on the interplay between entropic and energetic interactions. Thin glassy films arecritical for the success of nanolithography. For that we have to understand the effect of confinement on the glass transitionbehavior in order to guarantee the stability and integrity of the lithographic masks. Simulations aim to understand the fundamental differences in the densities of states of glass formers in bulk and under confinement. With the advent of bionanotechnology the structure and phase behavior of lipid membranes as models for cellular membranes at the nano scale length is of importance due to implications in understanding the role of the lipids in biochemical membrane processes

A physical based model to predict performance degradation of FinFET accounting for interface state distribution effect due to hot carrier injection

A physical based model for predicting the performance degradation of the FinFET is developed accounting for the interface state distribution effect due to hot carrier injection (HCI). The non-uniform distribution of interface state along the FinFET channel is first extracted by a forward gated-diode method and then reproduced by an empirical model. From this, a physical-based device model, which accounts for the interface state distribution effect, is developed to predict the performance degradation of FinFET. The result shows that the developed model not only matches well with the experimental data of FinFET in all operation regions, but also predicts the asymmetric degradation of saturation drain current in forward and reverse operation mode. Finally, the impact of HCI to a 6-T SRAM cell is simulated using HSPICE. (C) 2010 Elsevier Ltd. All rights reserved

Temperature dependence of the interface state distribution due to hot carrier effect in FinFET device

Temperature dependence of the interface state distribution due to hot carrier injection (HCl) effect in FinFET device is investigated in this paper. The interface state distribution along the FinFET channel at various temperatures is first extracted by measuring the generation-recombination (G-R) current and then the shift of interface state density with temperature is analyzed. The result shows that the density of interface states increases with elevating temperature from 28 degrees C to 128 degrees C. While the change of generation rate slows down with rising temperature and the distribution region is insensitive to both stress time and temperature. Based on the measured data, an empirical Gaussian-like model is proposed to describe the interface state distribution along the FinFET channel and good agreements with experimental data are obtained. (C) 2010 Elsevier Ltd. All rights reserved

Generic Compact Model of Double-Gate MOSFETs Applicable to Different Operation Modes and Channels

In this paper, the Double-Gate MOSFET’s operation modes such as symmetric, asymmetric and independent-gate-operation are discussed and an idea for the generic compact model development is proposed. It is shown that the presented model predicts different operation modes and characteristics of DG MOSEETs with channels from heavily doped to intrinsic case, which are well verified by the 2-D numerical simulator

Numerical and experimental analysis of chloride and iodide transports in concrete under natural diffusion

This study investigates the natural diffusion laws of chloride ions and iodide ions in concrete and proposes their correlations during the process of diffusion. By measuring the free ion concentration at different exposure times and diffusion depths, time-varying laws related to the ion diffusion coefficient D and surface ion concentration Cs were proposed. The linear proportional relationship between two kinds of ions is explored and fills the relevant research gaps. Natural diffusion models of ions are established via the finite element software COMSOL and the adjustment parameters K and λ are innovatively proposed. Thus, this enables the effective conversion of the ion resistance permeability coefficients measured by the RCM and RIM methods, especially for the concrete containing chloride. The results of numerical calculation and experimental measurement have a strong correlation. Furthermore, a two-dimensional concrete model with different aggregates is used to simulate the ion diffusion characteristics. It is confirmed that the increase in aggregate volume ratio and tortuosity inhibited ion diffusion, and the ion concentration in the local area was greatly reduced