Search results for "Calculation Methods"

Towards an accurate molecular orbital theory for excited states : Ethene, butadiene, and hexatriene

1993

A newly proposed quantum chemical approach for ab initio calculations of electronic spectra of molecular systems is applied to the molecules ethene, trans‐1,3‐butadiene, and trans‐trans‐1,3,5‐hexatriene. The method has the aim of being accurate to better than 0.5 eV for excitation energies and is expected to provide structural and physical data for the excited states with good reliability. The approach is based on the complete active space (CAS) SCF method, which gives a proper description of the major features in the electronic structure of the excited state, independent of its complexity, accounts for all near degeneracy effects, and includes full orbital relaxation. Remaining dynamic ele…

The simulation library of the Belle II software system

2017

Modeling moderated proportional neutron counters using the Geant4 toolkit and the application to detection of fast neutron burst

2014

Comparison of large-angle production of charged pions with incident protons on cylindrical long and short targets

2009

The HARP Collaboration has presented measurements of the double-differential pi(+/-) production cross section in the range of momentum 100 MeV/c <= p <= 800 MeV/c and angle 0.35 rad <=theta <= 2.15 rad with proton beams hitting thin nuclear targets. In many applications the extrapolation to long targets is necessary. In this article the analysis of data taken with long (one interaction length) solid cylindrical targets made of carbon, tantalum, and lead is presented. The data were taken with the large-acceptance HARP detector in the T9 beam line of the CERN proton synchrotron. The secondary pions were produced by beams of protons with momenta of 5, 8, and 12GeV/c. The tracking and identific…

Understanding and Predicting Plutonium Alloys Aging: A Coupled Experimental and Theoretical Approach

2003

Understanding plutonium aging is a real challenge that requires developing very ambitious modeling and experiments. Examples of the different techniques developed and the physical values that can be reached are presented here.

Texture Effects on Zircaloy Oxidation : Experiment and Simulation

2002

Optimization of the contact surface shape of a shrinkage fit

1998

Amongst many processes existing today for the assembly of two cylindrical parts, the shrinkage fit is commonly used. However, in the calculation methods, the contact surfaces are assumed to be perfect. Therefore, in order to apply these, the standards necessitate very small geometrical tolerances. The objective of the present paper is to show that it is possible to take into account form defects by closely conformed contact modelling and to have a good representation of reality: form defects always exist to an increasing extent and are inherent in all kinds of manufacturing processes. Finally, it is shown that the presence of defects can be beneficial, allowing optimization from both a mech…

Jastrow-Correlated Configuration-Interaction Description of Light Nuclei

1999

This work describes recent progress of the UMIST-VALENCIA collaboration on the ab initio study of ground states of light nuclei using realistic forces. The method presented here constructs trial variational wave functions by superimposing a central Jastrow correlation on a state-dependent translationally invariant linearly correlated state, with very promising results.

Total and inelastic cross sections at LHC ats=7  TeVand beyond

2011

We discuss expectations for the total and inelastic cross sections at LHC CM energies $\sqrt{s}=7\text{ }\text{ }\mathrm{TeV}$ and 14 TeV obtained in an eikonal minijet model augmented by soft gluon ${k}_{t}$-resummation, which we describe in some detail. We present a band of predictions which encompass recent LHC data and suggest that the inelastic cross section described by two-channel eikonal models include only uncorrelated processes. We show that this interpretation of the model is supported by the LHC data.

Linear response strength functions with iterative Arnoldi diagonalization

2009

We report on an implementation of a new method to calculate RPA strength functions with iterative non-hermitian Arnoldi diagonalization method, which does not explicitly calculate and store the RPA matrix. We discuss the treatment of spurious modes, numerical stability, and how the method scales as the used model space is enlarged. We perform the particle-hole RPA benchmark calculations for double magic nucleus 132Sn and compare the resulting electromagnetic strength functions against those obtained within the standard RPA.