We have found in the past that this method can be used safely with the default cutoff. In the previous tutorial, the initial relaxation and the two volume restricted relaxations are performed independently. There are a spread of csi bond distances ranging from 3. Select the contcar file containing the optimized configuration, and drag and drop it into the builder to construct the geometries of the initial and final endpoints starting from bulk pt as discussed in the tutorial pt diffusion on pt surfaces using. In a quick and dirty volume scan, one performs a set of static calculations, only the. The following equations demonstrate the relationship between the different elastic constants, where. One of the software packages that uses dft to solve the quantum. Structure optimization through equationofstate fitting. However, some properties are not computable outofthe box. Ab initio based study of finitetemperature structural, elastic and.
In this tutorial, you will explore how quantumatk can be used as a graphical interface gui for vasp calculations. The structure is twodimensional and consists of two snse sheets oriented in the 0, 0, 1 direction. This is a very common questions from people who start to do calculations. Charting the complete elastic properties of inorganic. Bulk aln has a wurtzite hexagonal crystal structure space group p 6 3 mc. The method has also other advantages, for instance the bulk modulus is readily available. Set up and analyze vasp calculations with quantumatk. Dftfit uses abinito calculation to guide the optimization of potentials along with measured properties. Anyone familiar with bulk modulus calculations in vasp. The goal is to make it easier for users to include vasp calculations in their potential fitting. Calculate band gap with hse and vasp in this tutorial, we show how to calculate the electronic band gap through the hse hybrid functional using our web interface and the vasp.
I wonder what is the more reliable way to get the bulk modulus of a solid, given i have a set of energies at different lattice constants. Stress is applied to force per unit area, and strain is proportional change in length. Together with youngs modulus, the shear modulus, and hookes law, the bulk modulus describes a materials response to stress or strain. The bulk modulus drops by 2 orders of magnitude now it is about 24x too small and the equilibrium volume becomes even larger. In the present paper singlecrystal elastic constants calculated using first.
E youngs modulus, also known as modulus of elasticity. The obtained bulk modulus is off by about 2% which is very good. Fits the ev data to murnaghans equation of state and extracts equilibrium volumelattice parameter, bulk modulus and equilibrium energy to a summary file. Bulk modulus volumetric compression testing veryst. First principles prediction of the elastic, electronic. How to calculate bulk modulus from energyvolume data of unit cell. The total energy per atom and the bulk modulus per atom versus the averaged atomic volume are plotted in fig. Maybe, now you are familiar with bulk modulus calculation with vasp, but i just. A simplified method for thermal expansion calculations, debyegruneisen. Using the script and the parameter files given above a simple energyvolume calculation is possible. The components of c ij depend on the choice of coordinate system and lattice vectors, and in this work we have adopted the ieee standard 40 for all reported tensors. Executes vasp extracts energy, volume and cpu time for calculations prepares data files to plot ev curves. Density functional theory and the calculation of tcmg2o4. I am new to vasp calculation and have already done the bandstructure and density.
It is defined as the ratio between pressure increase and the resulting decrease in a materials volume. The bulk modulus of a material describes the volumetric deformation behavior of a material and is important when high hydrostatic pressures are present highpressure seals, deep sea exploration, etc. Bulk modulus is usually obtained from experimental or theoretical or semi theoretical theory with experimental work to fit energyvolume data. Energy vs volume volume relaxations and pulay stress. The current results are in the upper range of the bulk moduli results in the literature.
Setting up the vasp input for optimizing the bulk pt. The bulk modulus is a constant the describes how resistant a substance is to compression. The bulk modulus of scandia is evaluated by ab initio calculation, based on density functional theory, and compared with bulk modulus measurement on nearly fully dense scandia and with the value attained from the equation of state based on diamond anvil cell measurements. Bulk modulus is defined as the pressure increase needed to cause a given relative decrease in volume. Vasp can compute the ground state wavefunction and energy by searching all possible. Vasp computing bulk modulus of au micro and nano mechanics. This section presents an example to calculate bulk modulus of wurtzitetype sic. As such, a simple volume scan option 3, will allow for a good estimate of the equilibrium volume. From the fit you will get b0 bulk modulus, e0 total energy at minimum and v0. Calculating the bulk modulus of a fluid application center. Using mc2 cluster as an example, we provide the following vasp.
The lattice parameters, bulk modulus, and its pressure derivatives of these compounds have been obtained. In a quick and dirty volume scan, one performs a set of static calculations, only the volume of the cell is changed. In particular, you will learn how to easily create your structure and generate all the relevant vasp input files. Snse crystallizes in the orthorhombic pnma space group. Given two numbers, a the dividend and n the divisor, a modulo n abbreviated as a mod n is the remainder from the division of a by n. The goal of this script is to run vasp in iterations with different lattice constants. This plugin is the default output of the aiida plugin cutter, intended to help developers get started with their aiida plugins. The modulus of elasticity, also known as youngs modulus, is a material property and a measure of its stiffness under compression or tension. First principles prediction of the elastic, electronic, and optical. How does fit the birchmurganan equation for calculating bulk modulus using vasp code. How does fit the birchmurganan equation for calculating. Convert elastic modulus constants shear, youngs, bulk. G shear modulus, also known as modulus of rigidity.
Allowing the structure to relax at fixed volume changes the picture dramatically. The total energy can be fitted to some equation of states to obtain the equilibrium volume, the bulk modulus and so on. Here we give an example of how to use vasp to compute the bulk modulus of ldaau. This package is widely used in the computational research community to conduct firstprinciples calculations of materials properties such. Vasp can calculate secondorder elastic constants by strainstress relationships since version 5. There are a spread of sni bond distances ranging from 3. How can i calculate the bulk and shear modulus for a. The lattice parameters, bulk modulus, and its pressure derivatives of these. For instance, the expression 7 mod 5 would evaluate to 2 because 7 divided by 5 leaves a remainder of 2, while 10 mod 5 would evaluate to.
Calculate the ground state energy using you dft software of choice but make. Atomic simulation environment on triolith peter larsson. Calculation of the anisotropic coefficients of thermal. Cssni3 crystallizes in the orthorhombic pnma space group.
The resulting nodes are just grouped and we execute a calculation of the bulk modulus by fetching these nodes later. The majority of workflows currently included in atomate utilize the vienna abinitio software package vasp,, which enables plane wave density functional theory dft calculations of periodic systems. Ab initio calculation of elastic constants and derived. Most theoretical studies are obtained by uniformly changing the unit cells in global energy variations especially for isotropic systems where the molecules has a structure with cubic symmetries. To test the accuracy of our vasp and tdep calculations and the accuracy of our algorithm, we will compare our calculated values to experimental results for wellknown systems. Vasp, as well as other ab initio software, provides multiple settings and possibilities to. It can also be used to test the mechanical stability of any bulk system. Density functional theory and the calculation of tcmg 2 o 4 spinel lattice parameters a senior project by jon karlo macias. Here we can calculate for bulk modulus, pressure, initial volume and change in volume.
Once the bulk optimization is finished, the vasp output files will appear in the labfloor main window. We predict groundstate singlecrystalline youngs modulus and its. The result is a calculated set of c ij values that can be used to calculate properties such as the bulk modulus k and the shear modulus g, as described in table 1. The bulk modulus is calculated to be 233 gpa a factor 7 too large. Writing bulk modulus workchain aiidavasp documentation. I am new to vasp calculation and have already done the bandstructure and density of states calculation. The modulus of elasticity formula is simply stress divided by strain. Molecular dynamics simulation of montmorillonite and mechanical and thermodynamic properties calculations.
Thus, the agreement with experiment may indeed indicates the correctness of the ecs calculations. Writing bulk modulus script aiidavasp documentation. The electronic and magnetic structure of febased bulk. The total energy can be fitted to some equation of states to obtain the equilibrium volume, the bulk modulus etc. The structure is twodimensional and consists of two pto2 sheets oriented in the 0, 0, 1 direction. The obtained bulk modulus is off by about 2% which. The result is a calculated set of c ij values that can be used to calculate properties such as the bulk modulus k. The comparison shows that our calculated bulk modulus and lattice parameter are in good agreement with the experimental data and the previous theoretical values. We performed this calculation on mccc in serial model in.
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