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xsw841020

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[交流] 【求助】nband和occ 设置

ixc 7
nsppol 2
nbanddsto -1

# Crystalline aluminum : optimization of the lattice parameter
# at fixed number of k points and broadening.

#Definition of occupation numbers
occopt 2
nband 3 3 3 3 3 3 3 3
occ 1 1 0 1 1 0 1 1 0 1 1 0 1 0 0 1 0 0 1 0 0 1 0 0
tsmear 0.05

#Definition of the unit cell
acell 3*7.60          # This is equivalent to 7.60 7.60 7.60
rprim  0.0  0.5  0.5 # FCC primitive vectors (to be scaled by acell)
   0.5  0.0  0.5
   0.5  0.5  0.0

#Optimization of the lattice parameters
#optcell 1
#ionmov  3
ntime  10
dilatmx 1.05
#ecutsm  0.5

#Definition of the atom types
ntype 1          # There is only one type of atom
zatnum 13       # The keyword "zatnum" refers to the atomic number of the
               # possible type(s) of atom. The pseudopotential(s)
               # mentioned in the "files" file must correspond
               # to the type(s) of atom. Here, the only type is Aluminum


#Definition of the atoms
natom 1          # There is only one atom per cell
type 1          # This atom is of type 1, that is, Aluminum
xred             # This keyword indicate that the location of the atoms
               # will follow, one triplet of number for each atom
0.0  0.0  0.0    # Triplet giving the REDUCED coordinate of atom 1.

#Definition of the planewave basis set
ecut  6.0       # Maximal kinetic energy cut-off, in Hartree

#Definition of the k-point grid
kptopt 2       # Option for the automatic generation of k points, taking
               # into account the symmetry
ngkpt 2 2 2    # This is a 2x2x2 FCC grid, based on the primitive vectors
nshiftk 1       # of the reciprocal space. For a FCC real space lattice,
               # like the present one, it actually corresponds to the
               # so-called 4x4x4 Monkhorst-Pack grid, if the following shifts
               # are used :
shiftk 0.5 0.5 0.5
#    0.5 0.0 0.0
#    0.0 0.5 0.0
#    0.0 0.0 0.5

#Definition of the SCF procedure
nstep 10       # Maximal number of SCF cycles
toldfe 1.0d-6    # Will stop when, twice in a row, the difference
               # between two consecutive evaluations of total energy
               # differ by less than toldfe (in Hartree)
新手  我就想问下怎么得出 nband 和 occ 是这些呐  我看 tutorial 关于这怎么觉的不一样呐

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1楼 2010-12-23 20:42:45

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identation

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youzhizhe(金币+2):谢谢指导。 2010-12-23 23:37:24

nband在自洽计算的时候，如果是不考虑自旋绝缘体一般可指定为总电子数的一半，如果是金属一般要多余电子数目一半的百分之二十；
occ是电子占有数，考虑自旋的系统，你可以分别指定自旋上和自旋下的电子，两者总数和是电子数目；其实是自旋上和自旋下的occ分别是两个数组，应该是nband维的数组

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2楼2010-12-23 22:55:21

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mazuju028

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gzqdyouxia(金币+2):谢谢指点 2010-12-24 11:03:07

你这个例子中的nband,ocd的形式是由occopt=2决定的，当occopt=2时，表示可以标定每个k点对应的带数（nband）,还可以标定每个能级上电子占据数（occ）。
所以你的nband 3 3 3 3 3 3 3 3,表示的是4个K点，每个K点都有自旋向上和向下电子，且占据三个能级。
occ 1 1 0 1 1 0 1 1 0 1 1 0 1 0 0 1 0 0 1 0 0 1 0 0 表示4个K点上，自旋向上电子排布为1 1 0，自旋向下电子排布为1 0 0.

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3楼2010-12-24 09:06:12

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