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Dario Alfè - One of the best experts on this subject based on the ideXlab platform.
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phon a program to calculate phonons using the small Displacement Method
Computer Physics Communications, 2009Co-Authors: Dario AlfèAbstract:The program phon calculates force constant matrices and phonon frequencies in crystals. From the frequencies it also calculates various thermodynamic quantities, like the Helmholtz free energy, the entropy, the specific heat and the internal energy of the harmonic crystal. The procedure is based on the small Displacement Method, and can be used in combination with any program capable to calculate forces on the atoms of the crystal. In order to examine the usability of the Method, I present here two examples: metallic Al and insulating MgO. The phonons of these two materials are calculated using density functional theory. The small Displacement Method results are compared with those obtained using the linear response Method. In the case of Al the Method provides accurate phonon frequencies everywhere in the Brillouin Zone (BZ). In the case of MgO the longitudinal branch of the optical phonons near the centre of the BZ is incorrectly described as degenerate with the two transverse branches, because the non-analytical part of the dynamical matrix is ignored here; however, thermodynamic properties like the Helmholtz free are essentially unaffected.
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PHON: A program to calculate phonons using the small Displacement Method
COMPUT PHYS COMMUN, 2009Co-Authors: Dario AlfèAbstract:The program PHON calculates force constant matrices and phonon frequencies in crystals. From the frequencies it also calculates various thermodynamic quantities, like the Helmholtz free energy, the entropy, the specific heat and the internal energy of the harmonic crystal. The procedure is based on the small Displacement Method, and can be used in combination with any program capable to calculate forces on the atoms of the crystal. In order to examine the usability of the Method, I present here two examples: metallic Al and insulating MgO. The phonons of these two materials are calculated using density functional theory. The small Displacement Method results are compared with those obtained using the linear response Method. In the case of Al the Method provides accurate phonon frequencies everywhere in the Brillouin Zone (BZ). In the case of MgO the longitudinal branch of the optical phonons near the centre of the BZ is incorrectly described as degenerate with the two transverse branches, because the non-analytical part of the dynamical matrix is ignored here; however. thermodynamic properties like the Helmholtz free are essentially unaffected.Program summaryProgram title: PHONCatalogue identifier. AEDP_v1_0Program summary URL: http://cpc.cs.qub.ac.uk/sumniaries/AEDP_v1_0.htmlProgram obtainable from: CPC Program Library, Queen's University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 19 580No. of bytes in distributed program, including test data, etc.: 612 193Distribution format: tar.gzProgramming language: Fortran 90Computer: Any Unix, LinuxOperating system: UnixRAM: Depends on super-cell size, but usually negligibleClassification: 7.8External routines: Subprograms ZHEEV and DSYEV (Lapack); needs BLAS. A tutorial is provided with the distribution which requires the installation of the quantum-espresso package (http://www. quantum-espresso.org)Nature of problem: Stable crystals at low temperature can be well described by expanding the potential energy around the atomic equilibrium positions. The movements of the atoms around their equilibrium positions can then be described using harmonic theory, and is characterised by global vibrations called phonons, which can be identified by vectors in the Brillouin zone of the crystal, and there are 3 phonon branches for each atom in the primitive cell. Tile problem is to calculate the frequencies of these phonons for any arbitrary choice of q-vector in the Brillouin zone.Solution Method: The small Displacement Method: each atom in the primitive cell is displaced by a small amount, and the forces induced on all the other atoms in the crystal are calculated and used to construct the force constant matrix. Supercells of -100 atoms are usually large enough to describe the force constant matrix up to the range where its elements have fallen to negligibly small values. The force constant matrix is then used to compute the dynamical matrix at any chosen q-vector in the Brillouin zone, and the diagonalisation of the dynamical matrix provides the squares of the phonon frequencies.The PHON code needs external programs to calculate these forces, and it can be used with any program capable of calculating forces in crystals. The most useful applications are obtained with codes based on density functional theory, but there is no restriction on what can be used.Running time: Negligible, typically a few seconds (or at most a few minutes) on a PC. It can take longer if very dense meshes of q-points are needed, for example, to compute very accurate phonon density of states. (C) 2009 Elsevier B.V. All rights reserved.
Mitsutoshi Nakajima - One of the best experts on this subject based on the ideXlab platform.
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preparation of nanodispersions containing β carotene by solvent Displacement Method
Food Hydrocolloids, 2008Co-Authors: Henelyta S Ribeiro, Sosaku Ichikawa, Mitsutoshi NakajimaAbstract:The aim of this study is to produce β-carotene-loaded nanodispersions containing poly(d,l-lactic acid) (PLA) and poly(d,l-lactic-co-glycolic acid) (PLGA), that are widely used as polymer carriers, by solvent Displacement Method. Nanoparticles containing β-carotene were produced by interfacial deposition of the biodegradable polymer, due to the Displacement of acetone from the dispersed phase. Gelatin or Tween® 20 was used as stabilizing hydrocolloids in the continuous phase. β-carotene was entrapped in the polymeric matrix in the absence of any oily core material. In this kind of formulation, polymers assumed the function of protective colloids and possibly also chemical stabilization of the nanodispersed phase. For measuring the total β-carotene concentration of nanodispersions, β-carotene was extracted from the nanoparticles and analyzed spectrophotometrically. Analysis of the nanoparticle size and its distribution were carried out by laser diffraction spectrometry with polarization intensity differential scattering (PIDS) technology. Morphological examination of nanoparticles was performed by transmission electron microscopy (TEM). In all conditions, the β-carotene-enriched nanoparticles had a narrow size distribution.
Bin Ji - One of the best experts on this subject based on the ideXlab platform.
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Improvement of Spring Constant Calculation in Response Displacement Method
China Earthquake Engineering Journal, 2020Co-Authors: Bin JiAbstract:When the response Displacement Method is adopted for the seismic calculations of underground structures,the key is to determine the soil spring constant,as spring constant values directly affect the calculation results. Based on the existing static finite element Method of calculating the spring constant,six variations of this Method are designed through different applications of force,and their calculation results are compared. The calculation results of the whole solution and the whole simultaneous solution of the radial and tangential spring constant Methods should be dangerous,the single solution and the single simultaneous solution of the horizontal and vertical spring constant Methods possess high computational precision,and the calculation results of the whole solution and the whole simultaneous solution of the horizontal and vertical spring constant Methods show be safe.
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Sensitivity Analysis of the Parameters of Response Displacement Method
Journal of Disaster Prevention and Mitigation Engineering, 2020Co-Authors: Bin JiAbstract:As the complicated calculation parameters of the response Displacement Method,based on the basic case,a sensitivity analysis of four calculation parameters(coefficient of the spring,ground deformation,ground shear force,inertia force)were conducted,and the Methods for obtaining the parameters and the error sources of the Methods were summarized.Then,two calculation models were analysed.The conclusions show that the ground shear force has the greatest influence on the internal forces of the structure,and then is the ground deformation,the inertia force,and the coefficient of the spring.In the selection of the calculation model,there are two models,one is with spring at the top of the structure,the other is not.The internal forces of the former are greater than that of the latter.Ignoring the upper soil constraint effect leads to the calculation results being unsafe.
Henelyta S Ribeiro - One of the best experts on this subject based on the ideXlab platform.
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preparation of nanodispersions containing β carotene by solvent Displacement Method
Food Hydrocolloids, 2008Co-Authors: Henelyta S Ribeiro, Sosaku Ichikawa, Mitsutoshi NakajimaAbstract:The aim of this study is to produce β-carotene-loaded nanodispersions containing poly(d,l-lactic acid) (PLA) and poly(d,l-lactic-co-glycolic acid) (PLGA), that are widely used as polymer carriers, by solvent Displacement Method. Nanoparticles containing β-carotene were produced by interfacial deposition of the biodegradable polymer, due to the Displacement of acetone from the dispersed phase. Gelatin or Tween® 20 was used as stabilizing hydrocolloids in the continuous phase. β-carotene was entrapped in the polymeric matrix in the absence of any oily core material. In this kind of formulation, polymers assumed the function of protective colloids and possibly also chemical stabilization of the nanodispersed phase. For measuring the total β-carotene concentration of nanodispersions, β-carotene was extracted from the nanoparticles and analyzed spectrophotometrically. Analysis of the nanoparticle size and its distribution were carried out by laser diffraction spectrometry with polarization intensity differential scattering (PIDS) technology. Morphological examination of nanoparticles was performed by transmission electron microscopy (TEM). In all conditions, the β-carotene-enriched nanoparticles had a narrow size distribution.
Shuyun Jiang - One of the best experts on this subject based on the ideXlab platform.
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Optimum design of hybrid composite multi-ring flywheel rotor based on Displacement Method
Composites Science and Technology, 2012Co-Authors: Shaobo Wen, Shuyun JiangAbstract:A structure optimum design based on the Displacement Method has been performed to maximize the energy storage capacity of a hybrid composite multi-ring flywheel rotor. In the process of optimal design, the preload stress generated by interference assembly, the fiber material failure and the delamination between two adjacent rings under high speed rotation are all considered. Four types of the optimal schemes of energy storage capacity, energy per unit mass (. EPM), energy per unit volume (. EPV), energy per unit cost (. EPC) and energy per unit mass and cost (. EPMC) are proposed to satisfy the needs of different applications and optimal designs are carried out by using a sequential quadratic programming (. SQP). The optimal results show that all composed rings of the hybrid flywheel rotor can nearly reach the limits of strength in both radial and circumferential directions, and simultaneously the rotor is at the critical state of delamination. The radius parameters and the maximum allowed rotational speed of the hybrid composite flywheel are closely related to the optimal schemes. Considering the effects of angular acceleration and gravity on the delamination will result in the decreasing of energy storage capacities for four typical applications. © 2012 Elsevier Ltd.