PSTRESS: Difference between revisions
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{{TAGDEF|PSTRESS|[real]}} | {{TAGDEF|PSTRESS|[real]}} | ||
Description: | Description: Set the pressure in kB and add corrections to the stress tensor. | ||
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{ | During [[Ionic minimization|ionic minimization]], an energy term <math> E= V * \mathrm{PSTRESS} </math> is added to the total energy and the pressure set by {{TAG|PSTRESS}} is added to the diagonals of the stress tensor. This allows performing structure optimization at a specific external pressure. | ||
In molecular-dynamics calculations within the {{TAG|NpT ensemble}} | In [[Molecular dynamics|molecular-dynamics calculations]] within the {{TAG|NpT ensemble}}, {{TAG|PSTRESS}} controls the target pressure for the Parinello-Rahman{{cite|parrinello:prl:1980}}{{cite|parrinello:jap:1981}} barostat. The unit of {{TAG|PSTRESS}} is in kB. | ||
{{TAG|PSTRESS}} can also be used to correct errors caused by Pulay stress, i.e., errors in the calculated stress tensor caused by the incomplete basis set. To correct for Pulay-stress errors, set {{TAG|PSTRESS}} to the negative value of Pulay stress. The Pulay stress is computed by taking the difference between the external pressure at a very large cutoff and the desired cutoff. Look for the line 'external pressure' in the {{TAG|OUTCAR}} file. Before using this tag in this way, please read the section {{TAG | Energy vs volume Volume relaxations and Pulay stress}}. | |||
{{sc|PSTRESS|Examples|Examples that use this tag}} | {{sc|PSTRESS|Examples|Examples that use this tag}} | ||
Revision as of 09:38, 5 July 2022
PSTRESS = [real]
Description: Set the pressure in kB and add corrections to the stress tensor.
During ionic minimization, an energy term is added to the total energy and the pressure set by PSTRESS is added to the diagonals of the stress tensor. This allows performing structure optimization at a specific external pressure.
In molecular-dynamics calculations within the NpT ensemble, PSTRESS controls the target pressure for the Parinello-Rahman[1][2] barostat. The unit of PSTRESS is in kB.
PSTRESS can also be used to correct errors caused by Pulay stress, i.e., errors in the calculated stress tensor caused by the incomplete basis set. To correct for Pulay-stress errors, set PSTRESS to the negative value of Pulay stress. The Pulay stress is computed by taking the difference between the external pressure at a very large cutoff and the desired cutoff. Look for the line 'external pressure' in the OUTCAR file. Before using this tag in this way, please read the section Energy vs volume Volume relaxations and Pulay stress.