Spin unpolarized atom calculations

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Dear list members,

for benchmarking a semiempirical system, we would need to know the DFT energy of a Cl atom using spin-unpolarized calculations. Is there any way to get this energy out of NWChem?

Until now we tried the following:
  • ) Calculation of one atom using SMEAR and non-spin polarized mode, but NWCHEM refused to carry out this calculation.
  • ) Calculating a system of two Cl-atoms being 10 Angstrom apart from each other, using SMEAR and spin unpolarized calculation. NWCHEM calculates the system, but independen how far we put the atoms from each other, we always get the a single and a double degenerate for HOMO-2, HOMO-1 and HOMO. However, if the atoms do not "see" each other any more, one should obtain a threefold degenerate level instead (px, py and pz should be equivalent).

Is there any way to force NWCHEM to yield the solution with the threefold degenerate level?

Thank you in advance.

Bálint

  • Bert Forum:Admin, Forum:Mod, NWChemDeveloper, bureaucrat, sysop
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What you want is an average of configurations for the 3p^5, which would give you degenerate orbitals. NWChem, however, always calculates the ground state, i.e. you will get a 3p_x^2 3p_y^2 3p_z^1 (or one of the two other combinations) which does not give three degenerate orbitals.

Bert



Quote: Jun 30th 3:28 pm
Dear list members,

for benchmarking a semiempirical system, we would need to know the DFT energy of a Cl atom using spin-unpolarized calculations. Is there any way to get this energy out of NWChem?

Until now we tried the following:
  • ) Calculation of one atom using SMEAR and non-spin polarized mode, but NWCHEM refused to carry out this calculation.
  • ) Calculating a system of two Cl-atoms being 10 Angstrom apart from each other, using SMEAR and spin unpolarized calculation. NWCHEM calculates the system, but independen how far we put the atoms from each other, we always get the a single and a double degenerate for HOMO-2, HOMO-1 and HOMO. However, if the atoms do not "see" each other any more, one should obtain a threefold degenerate level instead (px, py and pz should be equivalent).

Is there any way to force NWCHEM to yield the solution with the threefold degenerate level?

Thank you in advance.

Bálint

  • Bert Forum:Admin, Forum:Mod, NWChemDeveloper, bureaucrat, sysop
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I.e., you want 1.66667 electrons in each px, py, and pz orbital...


Quote:Bert Jul 7th 12:26 am
What you want is an average of configurations for the 3p^5, which would give you degenerate orbitals. NWChem, however, always calculates the ground state, i.e. you will get a 3p_x^2 3p_y^2 3p_z^1 (or one of the two other combinations) which does not give three degenerate orbitals.

Bert



Quote: Jun 30th 3:28 pm
Dear list members,

for benchmarking a semiempirical system, we would need to know the DFT energy of a Cl atom using spin-unpolarized calculations. Is there any way to get this energy out of NWChem?

Until now we tried the following:
  • ) Calculation of one atom using SMEAR and non-spin polarized mode, but NWCHEM refused to carry out this calculation.
  • ) Calculating a system of two Cl-atoms being 10 Angstrom apart from each other, using SMEAR and spin unpolarized calculation. NWCHEM calculates the system, but independen how far we put the atoms from each other, we always get the a single and a double degenerate for HOMO-2, HOMO-1 and HOMO. However, if the atoms do not "see" each other any more, one should obtain a threefold degenerate level instead (px, py and pz should be equivalent).

Is there any way to force NWCHEM to yield the solution with the threefold degenerate level?

Thank you in advance.

Bálint


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