RKS calculation with Doublet Multiplicity, strange?
Natalie Austin
natalie... at gmail.com
Mon Oct 17 20:29:35 UTC 2016
Hello,
I was running a calculation (calculation 1) with an odd number of
electrons. The default multiplicity was set to doublet. This calculation
ran without the UKS tag.
I compared this calculation to one in which I included the UKS keyword in
the input (calculation 2). The electronic energies of each calc1 and cal 2
were comparable to 10E-7.
I found it strange that CP2K would run a system with an odd number of
electrons as RKS, is this because of the smearing?
Input:
&FORCE_EVAL
METHOD QS
&DFT
BASIS_SET_FILE_NAME BASIS_MOLOPT
POTENTIAL_FILE_NAME GTH_POTENTIALS
&MGRID
CUTOFF 500
REL_CUTOFF 60
NGRIDS 4
&END MGRID
&QS
EPS_DEFAULT 1.0E-14
MAP_CONSISTENT
&END QS
&SCF
SCF_GUESS ATOMIC
EPS_SCF 1.0E-8
MAX_SCF 500
ADDED_MOS 200
CHOLESKY INVERSE
&SMEAR ON
METHOD FERMI_DIRAC
ELECTRONIC_TEMPERATURE [K] 300
&END SMEAR
&DIAGONALIZATION
ALGORITHM STANDARD
&END DIAGONALIZATION
&MIXING
METHOD BROYDEN_MIXING
ALPHA 0.1
BETA 1.5
NBROYDEN 8
&END MIXING
&END SCF
&XC
&XC_FUNCTIONAL PBE
&END XC_FUNCTIONAL
&END XC
CHARGE -1
&POISSON
POISSON_SOLVER WAVELET
PERIODIC NONE
&END POISSON
# UKS .TRUE. => this is uncommented in the UKS calculation
&END DFT
Calculation 1:
DFT| Spin restricted Kohn-Sham (RKS) calculation
RKS
DFT| Multiplicity
2
DFT| Number of spin states
1
DFT| Charge
-1
Calculation 2
DFT| Spin unrestricted (spin-polarized) Kohn-Sham calculation
UKS
DFT| Multiplicity
2
DFT| Number of spin states
2
DFT| Charge
-1
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