pressure calculations for liquid Pb
Posted: Thu Jul 24, 2014 8:46 am
Hello
I am trying to compute pressure for liquid Pb running MD. I have 216 Pb atoms in the cubic box os side 19.25 Ang - which gives the correct liquid lead density at T=800K. The system is well equilibrated (20 ps VASP equilibration starting from the melted structure obtained via classical MD). I run Nose dynamics at T=800 and compute the average pressure along MD run.
When I use LDA the pressure is too low ~ -14 kB (should be physically zero for this T and density), if I use the same structure but employ PBE functional the pressure becomes ~+15kB (way too large). It looks wrong or I missing some physics here.
I would appreciate any help and advices,
Many thanks, Daniel.
I am trying to compute pressure for liquid Pb running MD. I have 216 Pb atoms in the cubic box os side 19.25 Ang - which gives the correct liquid lead density at T=800K. The system is well equilibrated (20 ps VASP equilibration starting from the melted structure obtained via classical MD). I run Nose dynamics at T=800 and compute the average pressure along MD run.
When I use LDA the pressure is too low ~ -14 kB (should be physically zero for this T and density), if I use the same structure but employ PBE functional the pressure becomes ~+15kB (way too large). It looks wrong or I missing some physics here.
I would appreciate any help and advices,
Many thanks, Daniel.