设置：
初始值收敛值结果
AMIX =0.0100；BMIX =0.0001 AMIX = 0.01; BMIX = 0.00 计算无误
AMIX = 0.1000；BMIX = 0.0010 AMIX = 0.10; BMIX = 0.00 计算无误
AMIX =0.20; BMIX = 0.01 AMIX =0.20; BMIX = 0.01 计算无误
AMIX=0.2、BMIX=0.001 AMIX=0.2、BMIX=0.001 计算无误
AMIX=0.3、BMIX=0.1 AMIX=0.3、BMIX=0.1 计算无误
AMIX=0.4 AMIX = 0.40; BMIX = 1.00 静态log: WARNING in EDDRMM: call to
ZHEGV failed, returncode = 6 3 **,能带
一样
AMIX=0.02 AMIX = 0.02; BMIX = 1.00 计算无误
AMIX=0.1 AMIX = 0.10; BMIX = 1.00 静态log: WARNING in EDDRMM: call to
ZHEGV failed, returncode = 6 3 **,能带
一样
AMIX=0.3 AMIX = 0.30; BMIX = 1.00 静态log: WARNING in EDDRMM: call to
ZHEGV failed, returncode = 6 3 **,能带
一样
BMIX=0.0001 AMIX = 0.40; BMIX = 0.00 计算无误
以上参数设置，得到的能带图都一样，如下图:
综上：设置AMIX=0.2（或0.3）,BMIX默认（省事，等于1.0），可以保证计算过程无误。
还需进一步调整其他参数，算出正确的能带。
警告：算1QL弛豫、静态、能带时，都有这个提示：
ADVICE TO THIS USER RUNNING 'V ASP/V AMP' (HEAR YOUR MASTER'S VOICE ...): You have a (more or less)
'small supercell' and for smaller cells it is recommended to use the reciprocal-space projection scheme! The real space optimization is not efficient for small cells and it is also less accurate ... Therefore set LREAL=.FALSE. in the INCAR file
对策：对于较小的晶胞（原子数小于20），设置LREAL=.FALSE.，计算结果比较精确。
而对于较大的晶胞，设置LREAL=Auto，这样计算速度比较快。
本体系含原子5个，INCAR中LREAL=Auto。
设置所有INCAR中的
LREAL=.FALSE.，重新算一遍。
对于1QL 2QL 3QL原子数分别为5、10、15，LREAL=.False.
对于4QL 5QL 6QL原子数分别为20、25、30，LREAL=Auto
自旋轨道耦合计算时，静态和能带计算中出现的错误：
ERROR: non collinear calculations require that V ASP is compiled without the flag -DNGXhalf and -DNGZhalf
分析：V ASP手册中关于自旋轨道耦合计算的描述（翻译版）：
•
【SAXIS =自旋轴方向；MAGMOM= 每个原子的初始磁矩值】
2) 不要忘记
to include SOC, please
1) add the following lines to INCAR
LNONCOLLINEAR=.True.
LSORBIT=.True.
SAXIS = # please give the spin quantization axis here, like 0 0 1 for the z-axis)
MAGMOM= # please give a triplet of numbers for each atom here, and please have a look at the manual (chapter non-collinear calculations and spin-orbit tag) on how the direction of the magnetic moments has to be defined with respect to the spin-quantization axis)
LORBMOM=.True.
ISYM= -1
2）不要忘记如果你用的vasp不包含任何预编译程序命令-DNGXhalf, -DNGZhalf, -DwNGXhalf, -DwNGZhalf ，你必须重新编译vasp，因为这些参数通常对于非线性磁性计算是必要的，在DOSCAR中的第二块数据包含了E和4列s,p,d，如下：rho, m_x, m_y, m_z ，
2) don't forget that you may have to re-compile vasp without any of the precompiler (CPP) flags set: -DNGXhalf, -DNGZhalf, -DwNGXhalf, -DwNGZhalf , as necessary for non-collinear runs in general for non-collinear magnetism, the second block of data in DOSCAR contains E, and 4 columns for each, s,p,d, giving:
rho, m_x, m_y, m_z
with m....magnetisation，it makes absolutely NO SENSE to set ISPIN=2 (up and down) for non-clollinear runs, therfore this tag is ignored when it s read from INCAR.
Symbol Description
Γ Center of the Brillouin zone
Simple cube
M Center of an edge
R Corner point
X Center of a face
Face-centered cubic
K Middle of an edge joining two hexagonal faces
L Center of a hexagonal face
U Middle of an edge joining a hexagonal and a square face
W Corner point
X Center of a square face
Body-centered cubic
H Corner point joining four edges
N Center of a face
P Corner point joining three edges
Hexagonal
A Center of a hexagonal face
H Corner point
K Middle of an edge joining two rectangular faces
L Middle of an edge joining a hexagonal and a rectangular face
M Center of a rectangular face
1) it does not look to me as if the magnetic convergence is particularly bad. (please dont compare the moments stemming from
the augmentation to the total moments).
have you decreased AMIX,BMIX, AMIX_MAG and BMIX_MAG for this run?
2)the mixing parameters must not have any influence on the converged total energies.
3) if your system has a magnetic moment, you have to set ISPIN.
unless you set LNONCOLLINEAR explicitely , collinear magnetism is assumed by default, there is nothing to be specified in extra (except from starting with FM or AFM configuration by choosing the MAGMOMs accordingly)
4) please in any case check if the convergence of ALL ionic steps is bad. (consider that it may be possible that you relaxed into an unreasonable geometry which does not converge electronically).
without knowing further details, I would recommend to try the following:
please keep the low mixing parameters check if the k-mesh is converged try if a different BZ-integration (ISMEAR=1) and slightly larger smearing (SIGMA) helps set LMAXMIX=6 if your system contains d-elements
ISYM-tag and SYMPREC-tag
ISYM = 0|1|2|3
Default 1
switch symmetry on (1, 2 or 3) or off (0).
For ISYM=2 a more efficient, memory conserving symmetrisation of the charge density is used. This reduces memory requirements in particular for the parallel version. ISYM=2 is the default if PAW data sets are used.
ISYM=1 is the default if VASP runs with US-PP’s.
For ISYM=3, the forces and the stress tensor only are symmetrized, whereas the charge density is left unsymmetrized (VASP.5.1 only).
This option might be useful in special cases, where charge/orbital ordering lowers the crystal symmetry, and the user wants to conserve 【保存, 保藏】the symmetry of the positions during relaxation.
However, the flag must be used with great caution, since a lower symmetry due to charge/orbital ordering, in principle also requires to sample the Brillouin zone using
a k-point mesh compatible with the lower symmetry caused by charge/orbital ordering.
The program determines automatically the point group symmetry and the space group according to the POSCAR file and the line MAGMOM in the INCAR file.
The SYMPREC-tag (VASP.4.4.4 and newer versions only) determines how accurate the positions in the POSCAR file must be. The default is 10−5, which is usually suffiently large even if the POSCAR file has been generated with a single precision
program.
Increasing the SYMPREC tag means, that the positions in the POSCAR file can be less accurate.
During the symmetry analysis, VASP determines
• the Bravais lattice type of the supercell,
• the point group symmetry and the space group of the supercell wit h basis (static and dynamic) - and prints the names
of the group (space group: only ’family’),
• the type of the generating elementary (primitive) cell if the supercell is a non-primitive cell,
• all ’trivial non-trivial’ translations (= trivial translatio ns of the generating elementary cell within the supercell) —needed for symmetrisation of the charge,
• the symmetry-irreducible set of k-points if automatic k-mesh generation was used
and additionally the symmetry irreducible set of tetrahedra if the tetrahedron method was chosen together with the automatic k-mesh generation and of course also the corresponding weights (’symmetry degeneracy’),
• and tables marking and connecting symmetry equivalent ions.The symmetry analyses is done in four steps:
• First the point group symmetry of the lattice (as supplied by the user) is determined.
• Then tests are performed, whether the basis breaks symmetry. Accordingly these symmetry operations are removed.
• The initial velocities are checked for symmetry breaking.
• Finally, it is checked wheter MAGMOM breaks the symmetry. Correspondingly themagnetic symmetry group is determined (VASP.4.4.4 and newer releases only; if you use older version please also see section 6.12). The program symmetrises automatically:
• The t otal 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.。
