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General Questions and Answers / How much memory will it require to run the script?
« on: February 15, 2018, 07:07 »I am trying to run a script. How much memory will it require? The calculation unfortunately stops in the middle.
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I am trying to run a script. How much memory will it require? The calculation unfortunately stops in the middle.
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General Questions and Answers / Phase Transition Pressure
« on: September 20, 2017, 08:58 »
Hello everyone,
1. How does the common tangent drawn between Energy-Volume Curves of two phases of the same compound give the transition pressure between the two phases thermodynamically?
2. I read that the slope of the tangent gives the transition pressure. The steeper the slope, the transition pressure becomes smaller. What is the relationship between the slope of the common tangent and the transition pressure in GPa?
1. How does the common tangent drawn between Energy-Volume Curves of two phases of the same compound give the transition pressure between the two phases thermodynamically?
2. I read that the slope of the tangent gives the transition pressure. The steeper the slope, the transition pressure becomes smaller. What is the relationship between the slope of the common tangent and the transition pressure in GPa?
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General Questions and Answers / Prediction of a strucure
« on: September 10, 2017, 22:28 »
Sir
I have experimental lattice parameters of a structure at 12 GPa (stable at this pressure) . How can i model the structure at 0 GPa from the above information?
I have experimental lattice parameters of a structure at 12 GPa (stable at this pressure) . How can i model the structure at 0 GPa from the above information?
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General Questions and Answers / Space Group Change after creating a defect compound
« on: September 7, 2017, 08:27 »
Sir ,
To model a defect compound (disordered rocksalt), i used repeat cell . I found that after building the structure with vacancies involved , the space group changes .
1. Will this change not affect the results of any calculation ?
2. If elastic constants are calculated, how to analyse the result if there are more independent elastic constants than the rocksalt structure?
To model a defect compound (disordered rocksalt), i used repeat cell . I found that after building the structure with vacancies involved , the space group changes .
1. Will this change not affect the results of any calculation ?
2. If elastic constants are calculated, how to analyse the result if there are more independent elastic constants than the rocksalt structure?
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General Questions and Answers / Phase transition
« on: September 6, 2017, 15:54 »
Sir
I want to study pressure induced phase transition of a defect chalcopyrite (low pressure phase). The high pressure phase is a disordered structure with fractional occupancy of atoms ( for this i want to build using supercell 2X2X2). More importantly, I want to calculate the transition pressure between the two phases.
1. In order to do this, do i have to build a supercell of the same size for the low pressure phase to compare the enthalpies with the high pressure phase and predict the required transition pressure ?
2. For this, do i have to use LDA or GGA?
I want to study pressure induced phase transition of a defect chalcopyrite (low pressure phase). The high pressure phase is a disordered structure with fractional occupancy of atoms ( for this i want to build using supercell 2X2X2). More importantly, I want to calculate the transition pressure between the two phases.
1. In order to do this, do i have to build a supercell of the same size for the low pressure phase to compare the enthalpies with the high pressure phase and predict the required transition pressure ?
2. For this, do i have to use LDA or GGA?
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General Questions and Answers / Keeping script in Queue
« on: May 31, 2017, 20:00 »
Sir
Is it possible to keep a script in queue while other script is running and just after the job is completed the script in queue automatically starts
running?
Is it possible to keep a script in queue while other script is running and just after the job is completed the script in queue automatically starts
running?
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General Questions and Answers / Relation between Pressure applied and Density Mesh cut-off
« on: May 24, 2017, 12:40 »
Hello sir
Is there any relationship between pressure applied to a configuration and the mesh cut -off? Please explain
Is there any relationship between pressure applied to a configuration and the mesh cut -off? Please explain
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General Questions and Answers / Pressure effect
« on: May 23, 2017, 08:56 »
hello Sir
By applying different pressure on a crystal structure i have calculated different Enthalpies at those pressure(Using OptimizeGeometry Block). I am getting a linear response upto a certain pressure(which is correct) but after that it is becoming zig zag.How can i rectify the problem? I am using the same Density cut-off and k-pts
By applying different pressure on a crystal structure i have calculated different Enthalpies at those pressure(Using OptimizeGeometry Block). I am getting a linear response upto a certain pressure(which is correct) but after that it is becoming zig zag.How can i rectify the problem? I am using the same Density cut-off and k-pts
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General Questions and Answers / Pressure induced Enthalpy Calculation
« on: May 18, 2017, 11:24 »
Sir
By applying different pressure on a crystal structure i have calculated different Enthalpies at those pressure. I am getting a linear response upto a certain pressure(which is correct) but after that it is becoming zig zag.How can i rectify the problem?
By applying different pressure on a crystal structure i have calculated different Enthalpies at those pressure. I am getting a linear response upto a certain pressure(which is correct) but after that it is becoming zig zag.How can i rectify the problem?
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General Questions and Answers / DOS CALCULATION ERROR
« on: May 8, 2017, 09:50 »
Sir
I run a DOS calculation on the given script given below . I got an error which is in the log file. Please point me out the mistakes. Is it the problem with memory.? I have run a similar script with 25p.c Aluminium calculated with a different Density cut -off and in that, there is no error.
I run a DOS calculation on the given script given below . I got an error which is in the log file. Please point me out the mistakes. Is it the problem with memory.? I have run a similar script with 25p.c Aluminium calculated with a different Density cut -off and in that, there is no error.
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General Questions and Answers / Calculation using Primitive cell or Conventional Cell
« on: February 6, 2017, 10:58 »
Hi everyone,
I tried to find the bandstructure of a primitive cell and i got an expected result. But when i tried using a conventional cell of the same crystal, i got a different bandstructure and the bandgap. Furthermore , the brilioun zone route reduces to only two points G and X. Is it because the number of atoms increased??.Please explain. And which cell should we use (primitive/conventional) for calculation of properties?
I tried to find the bandstructure of a primitive cell and i got an expected result. But when i tried using a conventional cell of the same crystal, i got a different bandstructure and the bandgap. Furthermore , the brilioun zone route reduces to only two points G and X. Is it because the number of atoms increased??.Please explain. And which cell should we use (primitive/conventional) for calculation of properties?
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General Questions and Answers / Structural Optimization to find equilibrium Lattice parameters
« on: February 2, 2017, 14:28 »
Hi everyone, 
I am very new to DFT, and I want to calculate the equilibrium lattice constants of a tetragonal crystal system. The experimental lattice parameters are a=5.92 (angstrom) and c=11.8(angstrom). So, for plotting the total energy Vs Lattice constant graph, I vary the value of 'a' by a step of 0.02 Angstrom from 4.72 Angstrom to 6.12 Angstrom with a fixed value of c. But i am getting an increasing curve which has a minimum at 4.72 Angstrom which is far different from the experimental value and other theoretical values. Atomic positions are correct and the space group too. Should c/a ratio needs to be fixed while changing the values of 'a'?Please help .
I am very new to DFT, and I want to calculate the equilibrium lattice constants of a tetragonal crystal system. The experimental lattice parameters are a=5.92 (angstrom) and c=11.8(angstrom). So, for plotting the total energy Vs Lattice constant graph, I vary the value of 'a' by a step of 0.02 Angstrom from 4.72 Angstrom to 6.12 Angstrom with a fixed value of c. But i am getting an increasing curve which has a minimum at 4.72 Angstrom which is far different from the experimental value and other theoretical values. Atomic positions are correct and the space group too. Should c/a ratio needs to be fixed while changing the values of 'a'?Please help .
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