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Strange Mulliken Populations using new PAO in NEGF Date: 2011/10/12 17:43 Name: Sarah Jones Hi, I have been using the new PAO/VPS for NEGF calculations and have found strange behaviour with the Mulliken Population. I am using Al7.0 and C5.0 PAO and the PBE functional. After the NEGF converges (NormRD < 1.0e-06), the Mulliken Population gives a total of 1703.8 electrons, when the ideal neutral value is 1025. L0 and R0 regions are the worst affected, for example there are Al with a negative number of s electrons and over 40 p electrons, while some C have 1 electron and others 7. I have carried out the same calculation with the 06 PAO/VPS have not seen this kind of behaviour. I would appreciate any help fixing this. Thanks, Sarah

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Re: Strange Mulliken Populations using new PAO in NEGF ( No.1 ) Date: 2011/10/12 18:36 Name: T.Ozaki Hi, I guess that this is not a pseudopotential issue, but a local trap problem in the SCF calculation as described in the paper (PRB 81, 035116 (2010)). If your problem is the case, a little modification of code may improve the situation. To do that, you can modify a source TRAN_DFT.c. In a 214 line of TRAN_DFT.c, you may find if (3<iter || SucceedReadingDMfile==1){ If you modify the number '3' to a larger number e.g. '15', the conventional eigensolver is employed up to 14 SCF iterations. The treatment tends to avoid such a local trap problem. (The number will be controllable through the input file in the next version of OpenMX) Also, a modest charge mixing by tuning SCF parameters may avoid the local trap problem. Regards, TO Re: Strange Mulliken Populations using new PAO in NEGF ( No.2 ) Date: 2011/10/18 17:55 Name: Sarah Jones Hi, Thanks for your prompt reply. I changed "if (3<iter || SucceedReadingDMfile==1){" to "if (15<iter || SucceedReadingDMfile==1){", but as soon as the NEGF starts I get similar results as before except that there are now Al atoms with a negative number of electrons: Atom 87 MulP -0.3545-0.3545 sum -0.7089 I have tried the following for SCF mixing: scf.Mixing.Type rmm-diisk scf.Init.Mixing.Weight 0.001 scf.Min.Mixing.Weight 0.001 scf.Max.Mixing.Weight 0.2 scf.Kerker.factor 6 scf.Mixing.History 20 scf.Mixing.StartPulay 10 scf.Mixing.EveryPulay 5 scf.Mixing.Type rmm-diisk scf.Init.Mixing.Weight 0.001 scf.Min.Mixing.Weight 0.001 scf.Max.Mixing.Weight 0.03 scf.Kerker.factor 6 scf.Mixing.History 20 scf.Mixing.StartPulay 10 scf.Mixing.EveryPulay 1 I am unsure what to change for the mixing parameters, as these have always worked with the older PAOs and any advice would be appreciated. Thanks, Sarah

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