VASP自旋轨道耦合计算错误汇总(5)

?The initial velocities are checked for symmetry breaking.

?Finally,it is checked wheter MAGMOM breaks the symmetry.Correspondingly themagnetic symmetry group is determined (VASP.4.4.4and newer releases only;if you use older version please also see section6.12).The program symmetrises automatically:

?The total charge density according to the determined space group

?The forces on the ions according to the determined space group.

?The stress tensor according to the determined space group

Why is symmetrisation necessary:Within LDA the symmetry of the supercell and the charge density are always the same.

This symmetry is broken,because a symmetry-irreducible set of k-points is used for the calculation.

To restore the correct charge density and the correct forces it is necessary to symmetrise these quantities.

It must be stressed that VASP does not determine the symmetry elements of the primitive cell.If the supercell has a lower symmetry than the primitive cell only the lower symmetry of the supercell is used in the calculation.In this case one should

not expect that forces that should be zero according to symmetry will be precisely zero in actual calculations.

The symmetry of the primitive cell is in fact broken in several places in VASP:

?local potential:

In reciprocal space,the potential V(G)should be zero,if G is not a reciprocal lattice vector of the primitive cell.

For PREC=Med,this is not guaranteed due to”aliasing”or wrap around and the charge density(and therefore the Hatree potential)might violate this point.But even for PREC=High,small errors are introduced,because the exchange correlation potential Vxc is calculated in real space.

?k-points:

In most cases,the automatic k-point grid does not have the symmetry of the primitive cell.

错误：

internal ERROR:DEPLE:IRDMAX must be increased to0

internal ERROR:DEPLE:IRDMAX must be increased to0

错误：

ERROR FEXCF:supplied exchange-correlation table is too small,maximal index:9344428

计算soc能带时，选择ISTART=1，即读入静态计算得到的WA VECAR

能带计算出错：

ERROR:while reading WA VECAR,plane wave coefficients changed16135