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Materials Studio: CASTEP Guide

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Materials Studio: CASTEP Guide CASTEP GUIDE MATERIALS STUDIO 2019 Copyright Notice ©2018 Dassault Systèmes. All rights reserved. 3DEXPERIENCE, the Compass icon and the 3DS logo, CATIA, SOLIDWORKS, ENOVIA, DELMIA, SIMULIA, GEOVIA, EXALEAD, 3DVIA, 3DSWYM, BIOVIA, NETVIBES, IFWE and 3DEXCITE, are commercial trademarks or registered trademarks of Dassault Systèmes, a French "société européenne" (Versailles Commercial Register # B 322 306 440), or its subsidiaries in the U.S. and/or other countries. All other trademarks are owned by their respective owners. Use of any Dassault Systèmes or its subsidiaries trademarks is subject to their express written approval. Acknowledgments and References To print photographs or files of computational results (figures and/or data) obtained by using Dassault Systèmes software, acknowledge the source in an appropriate format. For example: "Computational results were obtained by using Dassault Systèmes BIOVIA software programs. BIOVIA Materials Studio was used to perform the calculations and to generate the graphical results." Dassault Systèmes may grant permission to republish or reprint its copyrighted materials. Requests should be submitted to Dassault Systèmes Customer Support, either by visiting https://www.3ds.com/support/ and clicking Call us or Submit a request, or by writing to: Dassault Systèmes Customer Support 10, Rue Marcel Dassault 78140 Vélizy-Villacoublay FRANCE Contents CASTEP 1 Setting up a calculation on an isolated Introduction 1 molecule 32 Additional Information 1 Requesting electronic, structural, and vibrational properties 33 Tasks in CASTEP 2 Manipulating files 49 CASTEP Energy task 3 Analyzing CASTEP results 51 CASTEP Geometry Optimization task 3 Displaying trajectory and chart data 51 Equation of state calculation 4 Visualizing volumetric data 53 Geometry optimization methods 5 Displaying band structure charts 58 CASTEP Dynamics task 5 Displaying core level spectra 59 Selecting the thermodynamic ensemble 5 Displaying density of states charts 60 Defining the time step 5 Calculating elastic constants 62 Constraints during dynamics 5 Visualizing Fermi surfaces 66 CASTEP Elastic Constants task 6 Visualizing vibrational spectra 66 CASTEP Transition State Search task 6 Displaying NMR results 67 Synchronous transit methods 7 Displaying optical properties 68 CASTEP TS Confirmation task 7 Displaying phonon dispersion and density CASTEP Properties 8 of states 70 Modeling disorder in solids 9 Displaying population analysis results 71 Mixture atoms 9 Calculating reaction kinetics 72 Technical limitations 9 Displaying the averaged potential chart for Setting up CASTEP calculations 10 work function calculations 73 Setting electronic options 10 Updating structure 73 Setting up a geometry optimization 22 Displaying thermodynamic properties 74 Setting up a molecular dynamics CASTEP jobs 76 calculation 24 Using CASTEP job control 76 Setting up a transition state calculation 26 Running CASTEP jobs in parallel 76 Setting up a transition state confirmation Remote CASTEP jobs 76 calculation 26 A sample CASTEP run 77 Setting up an elastic constants calculation 27 If a remote CASTEP job fails 79 Setting up an LDA+U calculation 28 Running CASTEP in standalone mode 80 Setting up a core hole calculation 29 CASTEP file formats 82 Setting up a work function calculation 30 CASTEP file formats - PARAM 83 Setting up a reaction kinetics calculation 31 CASTEP file formats - CELL 83 Page i | Materials Studio • CASTEP Guide CASTEP file formats - CASTEP 84 Estimated compressibility 112 CASTEP file formats - binary checkpoint TPSD geometry optimization 113 files 84 Damped molecular dynamics 113 CASTEP file formats - BANDS 84 Dynamics 113 CASTEP file formats - CST_ESP 84 Wavefunctions and density extrapolation 114 CASTEP file formats - task-specific files 84 Ensembles 115 CASTEP file formats - PHONON 85 Constraints 118 CASTEP file formats - TDDFT 85 Example 118 CASTEP file formats - PDOS_WEIGHTS 85 Core level spectroscopy 119 CASTEP file formats - CST_OME 85 Emission spectroscopy 119 CASTEP file formats - ORBITALS 86 Absorption spectroscopy 120 CASTEP file formats - CHDIFF 86 Core hole effects 120 CASTEP file formats - ELF 86 Energy broadening 120 CASTEP file formats - OTFG 86 Spin-orbit splitting 121 Reaction Kinetics Study Table 87 Phonon density of states 121 Theory in CASTEP 88 Electron localization function 121 CASTEP background theory 88 Formulation of electron localization Supercell approach 88 function 121 Fast Fourier transforms (FFT) in CASTEP 90 How to interpret ELF 123 Exchange-correlation functionals in CASTEP 91 Mulliken population analysis 123 Spin Orbit Coupling 93 Introduction 123 LDA+U 93 Formalism 123 Symmetry in CASTEP 94 The LCAO Basis Set 125 Pseudopotentials 94 Implementation details 125 Plane wave basis set 102 Interpreting the results 126 Self-consistent electronic minimization 104 Hirshfeld charge analysis 126 Disorder in solids 106 Calculating NMR shielding tensors using Disorder and first principles calculations 107 pseudopotentials 127 Limitations of VCA implementation in All-electron magnetic response with CASTEP 108 pseudopotentials 127 Test results 108 Calculation of perturbed wavefunctions 128 Geometry optimization 111 NMR properties of molecules and crystals 128 BFGS geometry optimization 111 NMR shielding tensor 128 Constraints 111 Sensitivity of NMR to calculation parameters 129 Non-linear constraints 112 NMR J-couplings 129 Page ii | Materials Studio • CASTEP Guide EPR G-tensor 130 Electron density selection 201 Optical properties 131 Electron density difference selection 202 Definition of optical constants 131 Electron localization function selection 202 DFT optics 133 Energy evolution selection 203 Evaluation of the dielectric constant 133 Fermi surface selection 203 Details of the calculation 133 IR spectrum selection 204 Limitations of the method 134 NMR selection 204 Sensitivity of optical properties to Optical properties selection 205 calculation parameters 135 Orbitals selection 206 TD-DFT optics 138 Phonon dispersion selection 207 Phonons 138 Phonon density of states selection 208 Practical schemes for phonon calculations 140 Population analysis selection 209 Interpolation schemes 141 Potentials selection 210 Symmetry analysis of vibrations 141 Reaction kinetics selection 211 Infrared spectra 141 Raman spectrum selection 211 Linear response 142 STM profile selection 212 Raman spectra 143 Structure selection 213 Thermodynamic calculations 144 Thermodynamic properties selection 213 Dialogs in CASTEP 147 Results file selector 214 CASTEP Calculation dialog 147 CASTEP keywords 215 Setup tab 147 CASTEP References 216 Electronic tab 162 CASTEP Density Mixing Options dialog 167 CASTEP Occupancy Options dialog 168 CASTEP Real Space Potentials dialog 172 Properties tab 174 CASTEP Phonon Density of States Options dialog 189 Job Control tab 192 CASTEP Job Files dialog 194 CASTEP Analysis dialog 195 Band structure selection 195 Core level spectroscopy selection 197 Density of states selection 198 Elastic constants selection 201 Page iii |Materials Studio • CASTEP Guide CASTEP Introduction CASTEP is a state-of-the-art quantum mechanics-based program designed specifically for solid-state materials science. CASTEP employs the density functional theory plane-wave pseudopotential method, which allows you to perform first-principles quantum mechanics calculations that explore the properties of crystals and surfaces in materials such as semiconductors, ceramics, metals, minerals, and zeolites. Typical applications involve studies of surface chemistry, structural properties, band structure, density of states, and optical properties. CASTEP can also be used to study the spatial distribution of the charge density and wavefunctions of a system. In addition, you can use CASTEP to calculate the full tensor of second-order elastic constants and related mechanical properties of a crystal (Poisson coefficient, Lamé constants, bulk modulus). The transition- state searching tools in CASTEP enable you to study chemical reactions in either the gas phase or on the surface of a material using linear synchronous transit/quadratic synchronous transit technology. These tools can also be used to investigate bulk and surface diffusion processes. CASTEP can be used effectively to study properties of both point defects (vacancies, interstitials, and substitutional impurities) and extended defects (for example grain boundaries and dislocations) in semiconductors and other materials. Furthermore, the vibrational properties of solids (phonon dispersion, total and projected density of phonon states, thermodynamic properties) can be calculated with CASTEP using either the linear response methodology or the finite displacements technique. The results can be used in various ways, for instance, to investigate the vibrational properties of adsorbates on surfaces, to interpret experimental neutron spectroscopy data or vibrational spectra, to study phase stability at high temperatures and pressures, and so on. The linear response method can also be used to calculate the response of a material to an applied electric field - polarizability for molecules and dielectric permittivity in solids - and to predict IR spectra. CASTEP can be used to calculate the properties required to analyze the results of solid-state NMR experiments, that is, chemical shifts and electric field gradients on atoms of interest. A detailed review of the CASTEP NMR formalism and numerous examples of practical applications are discussed in Bonhomme et al. (2012). The CASTEP
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