LNONCOLLINEAR: Difference between revisions

Latest revision as of 12:25, 26 September 2023

Default: LNONCOLLINEAR	= .False.
	= .True.	if spin-orbit coupling is included (LSORBIT=.True.)

Description: Switch on noncollinear magnetic calculations.

For noncollinear magnetic calculations, set LNONCOLLINEAR = True in the INCAR file and use the vasp_ncl executable. The electronic minimization treats the full 2x2 spin density^[1]

n_{\sigma \sigma '}(\mathbf {r} )=\sum _{n=1}^{N}\psi _{n\sigma }(\mathbf {r} )\psi _{n\sigma '}^{*}(\mathbf {r} ),

which is written to the CHGCAR file. In spinor space, the part of the spin density proportional to the 2x2 unit matrix corresponds to the charge density, and the part proportional to the vector of Pauli matrices is the magnetization density. This enables the consideration of noncollinear magnetic structures within spin-density-functional theory. MAGMOM sets the initial magnetic moments. Write the final magnetic moments by setting LORBIT.

It is possible to restart a noncollinear calculation from a previous nonmagnetic calculation (ISPIN=1 and LNONCOLLINEAR=F) or spin-polarized calculation (ISPIN=2) by reading WAVECAR or CHGCAR files. The magnetization of the spin-polarized calculation is interpreted to point along SAXIS (default: Cartesian direction ${\hat {z}}$ ). It is not possible to rotate the magnetic moment locally on selected atoms when restarting with a magnetization density. The magnetic configuration can globally be rotated with respect to the lattice by restarting with a different SAXIS.

In practice, we recommend performing noncollinear calculations in two steps:

First, calculate the nonmagnetic ground state and generate a WAVECAR and a CHGCAR file.
Second, read the WAVECAR and CHGCAR file, and supply initial magnetic moments using the MAGMOM tag.

We recommend setting GGA_COMPAT = False and LASPH= True for noncollinear calculations since this improves the numerical precision of calculations using the generalized-gradient approximation (GGA).

Consider setting AMIX_MAG and BMIX_MAG for better convergence when using density mixing.

The I_CONSTRAINED_M tag can constrain the on-site magnetic moments.

Supported as of VASP.4.5.

@@ Line 1: / Line 1: @@
-{{TAGDEF|LNONCOLLINEAR|.TRUE. {{!}} .FALSE.|.FALSE.}}
+{{TAGDEF|LNONCOLLINEAR|.True. {{!}} .False.}}
+{{DEF|LNONCOLLINEAR|.False.| |.True.|if spin-orbit coupling is included ({{TAG|LSORBIT}}{{=}}.True.)}}
-Description: {{TAG|LNONCOLLINEAR}} specifies whether fully non-collinear magnetic calculations are performed.
+Description: Switch on noncollinear magnetic calculations.
 ----
-Supported as of VASP.4.5.
-Setting {{TAG|LNONCOLLINEAR}} = .TRUE. in the {{TAG|INCAR}} file allows to perform fully non-collinear magnetic structure calculations. VASP is capable of reading {{TAG|WAVECAR}} and {{TAG|CHGCAR}} files from previous non-magnetic or collinear calculations, it is however not possible to rotate the magnetic field locally on selected atoms.
+For noncollinear magnetic calculations, set {{TAG|LNONCOLLINEAR}} = True in the {{TAG|INCAR}} file and use the <code>vasp_ncl</code> executable. The electronic minimization treats the full 2x2 spin density{{Cite|hobbs:prb:00}}
+:<math>
+n_{\sigma\sigma'}(\mathbf{r}) = \sum_{n=1}^N \psi_{n\sigma}(\mathbf{r})\psi^*_{n\sigma'}(\mathbf{r}),
+</math>
+which is written to the {{FILE|CHGCAR}} file. In spinor space, the part of the spin density proportional to the 2x2 unit matrix corresponds to the charge density, and the part proportional to the vector of Pauli matrices is the magnetization density.
+This enables the consideration of noncollinear magnetic structures within spin-density-functional theory. {{TAG|MAGMOM}} sets the initial magnetic moments. Write the final magnetic moments by setting {{TAG|LORBIT}}.
+It is possible to '''restart a noncollinear calculation''' from a previous nonmagnetic calculation ({{TAG|ISPIN}}=1 and {{TAG|LNONCOLLINEAR}}=F) or spin-polarized calculation ({{TAG|ISPIN}}=2) by reading {{TAG|WAVECAR}} or {{TAG|CHGCAR}} files. The magnetization of the spin-polarized calculation is interpreted to point along {{TAG|SAXIS}} (default: Cartesian direction <math>\hat z</math>). It is not possible to rotate the magnetic moment locally on selected atoms when restarting with a magnetization density. The magnetic configuration can globally be rotated with respect to the lattice by restarting with a different {{TAG|SAXIS}}.
+In practice, we recommend performing noncollinear calculations in two steps:
+*First, calculate the nonmagnetic ground state and generate a {{FILE|WAVECAR}} and a {{FILE|CHGCAR}} file.
+*Second, read the {{TAG|WAVECAR}} and {{TAG|CHGCAR}} file, and supply initial magnetic moments using the {{TAG|MAGMOM}} tag.
-Hence, in practice, we recommend to perform non-collinear calculations in two steps:
+We recommend setting {{TAG|GGA_COMPAT}} = False and {{TAG|LASPH}}= True for noncollinear calculations since this improves the numerical precision of calculations using the generalized-gradient approximation (GGA).
-*First, calculate the non magnetic groundstate and generate a {{TAG|WAVECAR}} and {{TAG|CHGCAR}} file.
-*Second, read the {{TAG|WAVECAR}} and {{TAG|CHGCAR}} file, and supply initial magnetic moments by means of the {{TAG|MAGMOM}} tag (compare {{TAG|MAGMOM}}).
-For a non-collinear setup, three values must be supplied for each ion in the {{TAG|MAGMOM}} line. The three entries correspond to the initial local magnetic moment for each ion in x, y and z direction respectively. The line
+Consider setting {{TAG|AMIX_MAG}} and {{TAG|BMIX_MAG}} for better convergence when using [[Density mixing|density mixing]].
-    MAGMOM = 1 0 0   0 1 0
+The {{TAG|I_CONSTRAINED_M}} tag can constrain the on-site magnetic moments.
-initialises the magnetic moment on the first atom in the x-direction, and on the second atom in the y direction. Mind, that the {{TAG|MAGMOM}} line supplies initial magnetic moments only if {{TAG|ICHARG}} = 2, or if the {{TAG|CHGCAR}} file contains only charge but no magnetisation density.
+Supported as of VASP.4.5.
-== Related Tags and Sections ==
+== Related tags and articles ==
 {{TAG|MAGMOM}},
-{{TAG|ICHARG}},
+{{TAG|LSORBIT}},
-{{TAG|LSORBIT}}
+{{TAG|SAXIS}},
+{{TAG|GGA_COMPAT}},
+{{TAG|LASPH}},
+{{TAG|AMIX_MAG}}, {{TAG|BMIX_MAG}},
 {{sc|LNONCOLLINEAR|Examples|Examples that use this tag}}
 ----
-[[The_VASP_Manual|Contents]]
-[[Category:INCAR]][[Category:Magnetism]]
+[[Category:INCAR tag]][[Category:Magnetism]][[Category:Noncollinear magnetism]]