Search results for "SIESTA"
showing 10 items of 12 documents
Ab initio calculations on the molecular structure of fluorocyanopolyynes
1998
Abstract The molecular structure of the first three members of the fluorocyanopolyynes was studied by ab initio Hartree-Fock calculations with a polarized double zeta basis set and at MP2 level with the same basis set. Alternating triple and single bonds were found; a theoretical estimate of rotational constants and dipole moments was performed and a comparison with the available experimental data was made. An analysis of the theoretical vibrational frequencies of the title compounds was carried out.
Metal Cluster — Surface Interaction: Simple Models and Ab Initio Calculations
1999
We review recent ab initio atomistic calculations on interactions between metal clusters and electronically inert (insulating) substrates. The model system is sodium clusters on the sodium-chloride (001) surface. This system provides an example of weak cluster-support interaction (physisorption) which can however be easily modified by introducing color centers at the surface, resulting in chemisorption of sodium adatom or cluster. The results obtained from atomistic calculations can be used for constructing simple jellium-type models for the adsorbed cluster. These models allow for systematic investigations in a large size-range of clusters on the shell structure, dimensionality, and stabil…
Ab initiocalculations of theHcenters in MgF2crystals
2012
MgF2 with rutile structure is important wide-gap optical material with numerous applications. We present and discuss the results of calculations for basic hole defects - interstitial F atoms (called also the colour H centres). This study is based on the large scale ab initio DFT calculations using hybrid B3PW exchange-correlation functional as implemented into CRYSTAL computer code. The electronic structure, atomic geometry, charge density distribution are calculated and discussed.
SIeSTA: From Concept Board to Concept Desktop
2011
Recently published social protection and dependence reports reaffirm that the elderly, the disabled, or those in situations of dependency objectively benefit from continuing to live at home with the assistance from direct family. Currently in Spain - amongst the elderly, or people in a situation of dependency - 8 out of every 10 people stay at home. The end result is that the direct family relations have the responsibility of performing 76% of the tasks during the daily routine where aid is needed. Associations for people with disabilities, however, not only report a lack of adequate aid services, but a lack of direct-family assistance as well. It is necessary, therefore, for an "evolution"…
Empathes: A general code for nudged elastic band transition states search
2022
Abstract An easy and flexible interface, Empathes (Extensible Minimum PATH EStimator), that allows to perform Nudged Elastic Band calculation for the determination of transition states is presented. The code is designed to be easily modified, in order to be associated with the user's preferred calculation software, even with those which implement composite approaches. In particular, the interfaces to Gaussian and Siesta programs are discussed in details, being the former only used for testing purpose, while the latter can be productively employed for transition states search with that commonly used density functional theory software for periodic calculations. Program summary Program Title: …
Ab initio calculations of the atomic and electronic structure of MgF2 (011) and (111) surfaces
2011
Abstract The results of ab initio slab calculations of surface relaxations, rumplings and charge distribution for the different terminations of the MgF2 (011) and (111) polar surfaces are presented and discussed. We have employed the computer code CRYSTAL with the Gaussian basis set and the hybrid B3PW exchange-correlation functional. Despite the ionic nature of the chemical bonding at both surfaces, a considerable decrease of the optical band gap is predicted (1.3 eV or 10%) for the (111) surface as compared to the bulk.
Structural, magnetic, dielectric and mechanical properties of (Ba,Sr)MnO3 ceramics
2017
The authors acknowledge the CPU time allocation at Academic Computer Centre CYFRONET AGH in Cracow. This work was supported in part by PL-Grid Infrastructure and the European Regional Development Fund under the Infrastructure and Environment Programme [grant number UDA-POIS.13.01-023/09-00]. The research was partially carried out with the equipment purchased thanks to the financial support of the European Regional Development Fund in the framework of the Polish Innovation Economy Operational Program (contract no. POIG.02.01.00-12-023/08). L. Vasylechko acknowledges partial support of the Ukrainian Ministry of Education and Sciences under the Projects ?RZE?, ?KMON?, and ICDD Grant-in-Aid pro…
Percentile Reference Charts for Selected Sleep Parameters for 20- to 80-Year-Old Healthy Subjects from the SIESTA Database. Referenzkurven fur ausgew…
2005
One of the aims of the SIESTA project was to establish a normative database of sleep parameters for healthy and sleep-disturbed patients. Reference data for sleep parameters in non-sleep-disturbed subjects are scarce and usually refer to means and standard deviations. However, since most of the parameters do not follow a Gaussian distribution, percentiles of the distribution provide more detailed information. The present results are based on data from 198 healthy, non-sleep-disturbed subjects (104 females) in the age range of 20 to 95 years. For every subject, two consecutive nights were polysomnographically recorded in one of the eight participating clinical centres. Percentile charts were…
Ab Initio Calculations of SrTiO3 (111) Surfaces
2012
The paper presents the results of calculations of SrTiO3 polar (111) surface relaxations and energetics using the ab initio code CRYSTAL and a hybrid description of exchange and correlation. Using a hybrid B3LYP approach, the surface relaxation has been calculated for the two possible Ti and SrO3 SrTiO3 (111) surface terminations. For both Ti and SrO3-terminated SrTiO3 (111) surfaces upper layer atoms, with the sole exception of SrO3-terminated surface Sr atom, relax inwards. The calculated surface relaxation energy for Ti-terminated SrTiO3 (111) surface is almost five times larger, than the surface relaxation energy for SrO3-terminated SrTiO3 (111) surface. The surface energy for Ti-termin…
Y:BaZrO3 Perovskite Compounds I: DFT Study on the Unprotonated and Protonated Local Structures
2011
Y-doped BaZrO(3) derivatives were studied by density functional theory (DFT) to investigate the local arrangements of the octahedral sites in Pm3m cubic frameworks. Single- and double substitution of zirconium by yttrium were considered, including in the presence of a nearby oxygen vacancy. Although the structural symmetry of undoped barium zirconate was not modified after yttrium doping, the presence of yttrium induced several differences in the oxygen sites around it, according to the local geometrical arrangement of yttrium in the host matrix. As an example, the differences between such oxygen sites were shown in the presence of a proton. In this case, different stabilization energies ch…