Spin-spiral calculations - Revision history

Huebsch: Huebsch moved page Construction:Spin-spiral calculations to Spin-spiral calculations without leaving a redirect

2026-06-22T08:18:23Z

Huebsch moved page Construction:Spin-spiral calculations to Spin-spiral calculations without leaving a redirect

← Older revision		Revision as of 08:18, 22 June 2026
(No difference)

Huebsch: Issue #16: proofreader fixes (Related-tags comma, Example 2 anchor, Step 1 paren, tt->code)

2026-06-22T08:13:56Z

Issue #16: proofreader fixes (Related-tags comma, Example 2 anchor, Step 1 paren, tt->code)

Huebsch: Issue #16: spin-spiral figure now single-panel; update caption

2026-06-19T11:55:48Z

Issue #16: spin-spiral figure now single-panel; update caption

← Older revision		Revision as of 11:55, 19 June 2026
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	This example uses a spin-spiral calculation to obtain the total energy of a flat spin spiral in a NiI<sub>2</sub> monolayer. The spin spiral is scanned along the {{TAG\|QSPIRAL}} path Γ–M–K–Γ to find the magnetic ground state. The triangular Ni sublattice is magnetically frustrated, which stabilizes an incommensurate spiral.		This example uses a spin-spiral calculation to obtain the total energy of a flat spin spiral in a NiI<sub>2</sub> monolayer. The spin spiral is scanned along the {{TAG\|QSPIRAL}} path Γ–M–K–Γ to find the magnetic ground state. The triangular Ni sublattice is magnetically frustrated, which stabilizes an incommensurate spiral.

	[[File:NiI2_spinspiral_structure.png\|thumb\|center\|~~650px~~\|~~Left: the 1T NiI<sub>2</sub> monolayer unit cell. Right: the~~ flat in-plane spin spiral at the computed Γ–M minimum '''Q''' = (0.214, 0, 0); the Ni moments rotate in the plane with period ''λ'' = 1/''Q'' ≈ 4.7 ''a~~'' along '''Q'~~''.]]		[[File:NiI2_spinspiral_structure.png\|thumb\|center\|600px\|The flat in-plane spin spiral at the computed Γ–M minimum '''Q''' = (0.214, 0, 0): the Ni moments rotate in the plane along '''Q''' with period ''λ'' = 1/''Q'' ≈ 4.7 ''a''.]]

	'''Structure''': A 1T (CdI<sub>2</sub>-type) NiI<sub>2</sub> monolayer, hexagonal ''a'' = 3.97 Å with ≈8 Å of vacuum ({{FILE\|POSCAR}}):		'''Structure''': A 1T (CdI<sub>2</sub>-type) NiI<sub>2</sub> monolayer, hexagonal ''a'' = 3.97 Å with ≈8 Å of vacuum ({{FILE\|POSCAR}}):

Huebsch: Issue #16: embed NiI2 structure + spin-spiral figure in Example 2

2026-06-19T11:49:48Z

Issue #16: embed NiI2 structure + spin-spiral figure in Example 2

← Older revision		Revision as of 11:49, 19 June 2026
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	=== Example 2: Spin-spiral energy of a NiI<sub>2</sub> monolayer ===		=== Example 2: Spin-spiral energy of a NiI<sub>2</sub> monolayer ===
	This example uses a spin-spiral calculation to obtain the total energy of a flat spin spiral in a NiI<sub>2</sub> monolayer. The spin spiral is scanned along the {{TAG\|QSPIRAL}} path Γ–M–K–Γ to find the magnetic ground state. The triangular Ni sublattice is magnetically frustrated, which stabilizes an incommensurate spiral.		This example uses a spin-spiral calculation to obtain the total energy of a flat spin spiral in a NiI<sub>2</sub> monolayer. The spin spiral is scanned along the {{TAG\|QSPIRAL}} path Γ–M–K–Γ to find the magnetic ground state. The triangular Ni sublattice is magnetically frustrated, which stabilizes an incommensurate spiral.

			[[File:NiI2_spinspiral_structure.png\|thumb\|center\|650px\|Left: the 1T NiI<sub>2</sub> monolayer unit cell. Right: the flat in-plane spin spiral at the computed Γ–M minimum '''Q''' = (0.214, 0, 0); the Ni moments rotate in the plane with period ''λ'' = 1/''Q'' ≈ 4.7 ''a'' along '''Q'''.]]

	'''Structure''': A 1T (CdI<sub>2</sub>-type) NiI<sub>2</sub> monolayer, hexagonal ''a'' = 3.97 Å with ≈8 Å of vacuum ({{FILE\|POSCAR}}):		'''Structure''': A 1T (CdI<sub>2</sub>-type) NiI<sub>2</sub> monolayer, hexagonal ''a'' = 3.97 Å with ≈8 Å of vacuum ({{FILE\|POSCAR}}):

Huebsch: Issue #16: embed spin-spiral energy figure in Example 2

2026-06-19T09:52:19Z

Issue #16: embed spin-spiral energy figure in Example 2

← Older revision		Revision as of 09:52, 19 June 2026
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	\| (0.133, 0.133, 0) \|\| Γ→K (minimum) \|\| −15.9		\| (0.133, 0.133, 0) \|\| Γ→K (minimum) \|\| −15.9
	\|}		\|}

			[[File:NiI2_spinspiral_energy.png\|thumb\|center\|500px\|Spin-spiral energy ''E''('''q''') − ''E''(Γ) of a monolayer NiI<sub>2</sub> along the Γ–M–K–Γ path (PBE). The minima at incommensurate '''q''' indicate a spin-spiral ground state; the Γ–M minimum near '''q''' ≈ (0.21, 0, 0) matches the experimental helimagnetic vector.]]

	The energy is lowest for an incommensurate spin spiral, not for the ferromagnet (Γ) or the high-symmetry M and K points, reflecting the frustration of the triangular Ni sublattice. Two shallow minima appear along inequivalent in-plane directions — near '''q''' ≈ (0.21, 0, 0) along Γ–M and '''q''' ≈ (0.13, 0.13, 0) along Γ–K — separated by a barrier of only ≈1 meV, and the spiral is stabilized by ≈16 meV per formula unit relative to the ferromagnet. The Γ–M minimum at '''q''' ≈ (0.21, 0, 0) is in good agreement with the helimagnetic propagation vector '''q''' = (0.220, 0, 0) measured for monolayer NiI<sub>2</sub> by spin-polarized scanning tunneling microscopy.{{cite\|miao:pnas:25}}		The energy is lowest for an incommensurate spin spiral, not for the ferromagnet (Γ) or the high-symmetry M and K points, reflecting the frustration of the triangular Ni sublattice. Two shallow minima appear along inequivalent in-plane directions — near '''q''' ≈ (0.21, 0, 0) along Γ–M and '''q''' ≈ (0.13, 0.13, 0) along Γ–K — separated by a barrier of only ≈1 meV, and the spiral is stabilized by ≈16 meV per formula unit relative to the ferromagnet. The Γ–M minimum at '''q''' ≈ (0.21, 0, 0) is in good agreement with the helimagnetic propagation vector '''q''' = (0.220, 0, 0) measured for monolayer NiI<sub>2</sub> by spin-polarized scanning tunneling microscopy.{{cite\|miao:pnas:25}}

Huebsch at 09:45, 19 June 2026

2026-06-19T09:45:00Z

Huebsch: Issue #16: Example 2 -> PBE results, experimental q comparison (Miao 2025), GPAW reference removed

2026-06-18T15:57:14Z

Issue #16: Example 2 -> PBE results, experimental q comparison (Miao 2025), GPAW reference removed

← Older revision		Revision as of 15:57, 18 June 2026
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	{{TAGBL\|MAGMOM}} = 2 0 0 0 0 0 0 0 0		{{TAGBL\|MAGMOM}} = 2 0 0 0 0 0 0 0 0

	A Γ-centered 12×12×1 k-mesh and Ni_pv and I PAW potentials were used. The total energy ''E''('''q''') is read from the {{FILE\|OUTCAR}}.		A Γ-centered 12×12×1 k-mesh and PBE Ni_pv and I PAW potentials were used. The total energy ''E''('''q''') is read from the {{FILE\|OUTCAR}}.

	'''Result''' — spin-spiral energy relative to the ferromagnetic state ('''q''' = Γ):		'''Result''' — spin-spiral energy relative to the ferromagnetic state ('''q''' = Γ):
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	\| (0, 0, 0) \|\| Γ (ferromagnetic) \|\| 0.0		\| (0, 0, 0) \|\| Γ (ferromagnetic) \|\| 0.0
	\|-		\|-
	\| (0.143, 0, 0) \|\| Γ→M \|\| ~~−22~~.7		\| (0.143, 0, 0) \|\| Γ→M \|\| −12.4
	\|-		\|-
	\| (0.214, 0, 0) \|\| Γ→M (minimum) \|\| ~~−29~~.7		\| (0.214, 0, 0) \|\| Γ→M (minimum) \|\| −14.5
	\|-		\|-
	\| (0.5, 0, 0) \|\| M \|\| +36.3		\| (0.5, 0, 0) \|\| M \|\| +40.2
	\|-		\|-
	\| (1/3, 1/3, 0) \|\| K \|\| ~~−12~~.5		\| (1/3, 1/3, 0) \|\| K \|\| +8.2
	\|-		\|-
	\| (0.133, 0.133, 0) \|\| Γ→K (minimum) \|\| ~~−32~~.9		\| (0.133, 0.133, 0) \|\| Γ→K (minimum) \|\| −15.9
	\|}		\|}

	The energy is lowest for an incommensurate spin spiral, not for the ferromagnet (Γ) or the M~~-point antiferromagnet~~. Two shallow minima appear along inequivalent in-plane directions — near '''q''' ≈ (0.21, 0, 0) along Γ–M and '''q''' ≈ (0.13, 0.13, 0) along Γ–K — separated by a barrier of only ≈3 meV, and the spiral is stabilized by ~~≈30~~ meV per formula unit relative to the ferromagnet. ~~This reproduces~~ the ~~qualitative result of the GPAW tutorial: a frustration-driven incommensurate ground state with two near~~-~~degenerate minima~~.		The energy is lowest for an incommensurate spin spiral, not for the ferromagnet (Γ) or the high-symmetry M and K points, reflecting the frustration of the triangular Ni sublattice. Two shallow minima appear along inequivalent in-plane directions — near '''q''' ≈ (0.21, 0, 0) along Γ–M and '''q''' ≈ (0.13, 0.13, 0) along Γ–K — separated by a barrier of only ≈1 meV, and the spiral is stabilized by ≈16 meV per formula unit relative to the ferromagnet. The Γ–M minimum at '''q''' ≈ (0.21, 0, 0) is in good agreement with the helimagnetic propagation vector '''q''' = (0.220, 0, 0) measured for monolayer NiI<sub>2</sub> by spin-polarized scanning tunneling microscopy.{{cite\|miao:pnas:25}}
	{{NB\|tip\|The exact position of the incommensurate minimum depends on the [[XC functional]], [[PAW potentials]], and proper convergence of k-mesh density, and cutoff energy.}}		{{NB\|tip\|The exact position of the incommensurate minimum depends on the [[XC functional]], [[PAW potentials]], and proper convergence of k-mesh density, and cutoff energy.}}
	== Magnon dispersion and exchange interactions ==		== Magnon dispersion and exchange interactions ==

Huebsch: /* Magnon dispersion and exchange interactions */

2026-06-18T13:39:00Z

Magnon dispersion and exchange interactions

← Older revision		Revision as of 13:39, 18 June 2026
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	* Restart each point from the same converged charge density ({{TAG\|ICHARG}} = 1) for consistency across the scan.		* Restart each point from the same converged charge density ({{TAG\|ICHARG}} = 1) for consistency across the scan.
	* The mapping assumes rigid local moments; verify that the local moment is roughly '''q'''-independent (in Example 2 it varies by only a few percent).		* The mapping assumes rigid local moments; verify that the local moment is roughly '''q'''-independent (in Example 2 it varies by only a few percent).
	{{NB\|mind\|The spin-spiral approach is incompatible with [[~~spin–orbit~~ coupling]] ({{TAG\|LSORBIT\|TRUE}}), because ~~spin–orbit~~ coupling breaks the spin-rotational symmetry that the generalized Bloch condition relies on.}}		{{NB\|mind\|The [[spin spirals\|spin-spiral approach]] is incompatible with [[spin-orbit coupling]] ({{TAG\|LSORBIT\|TRUE}}), because spin-orbit coupling breaks the spin-rotational symmetry that the generalized Bloch condition relies on.}}

	== Related tags and articles ==		== Related tags and articles ==

Huebsch at 13:38, 18 June 2026

2026-06-18T13:38:00Z

← Older revision		Revision as of 13:38, 18 June 2026
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	The energy is lowest for an incommensurate spin spiral, not for the ferromagnet (Γ) or the M-point antiferromagnet. Two shallow minima appear along inequivalent in-plane directions — near '''q''' ≈ (0.21, 0, 0) along Γ–M and '''q''' ≈ (0.13, 0.13, 0) along Γ–K — separated by a barrier of only ≈3 meV, and the spiral is stabilized by ≈30 meV per formula unit relative to the ferromagnet. This reproduces the qualitative result of the GPAW tutorial: a frustration-driven incommensurate ground state with two near-degenerate minima.		The energy is lowest for an incommensurate spin spiral, not for the ferromagnet (Γ) or the M-point antiferromagnet. Two shallow minima appear along inequivalent in-plane directions — near '''q''' ≈ (0.21, 0, 0) along Γ–M and '''q''' ≈ (0.13, 0.13, 0) along Γ–K — separated by a barrier of only ≈3 meV, and the spiral is stabilized by ≈30 meV per formula unit relative to the ferromagnet. This reproduces the qualitative result of the GPAW tutorial: a frustration-driven incommensurate ground state with two near-degenerate minima.
			{{NB\|tip\|The exact position of the incommensurate minimum depends on the [[XC functional]], [[PAW potentials]], and proper convergence of k-mesh density, and cutoff energy.}}
	{{NB\|tip\|The exact position of the incommensurate minimum depends on the functional, PAW potentials, k-mesh, and cutoff, so the numbers above reproduce the ''physics'' of the GPAW tutorial rather than identical values. Determining the orientation of the spiral plane additionally requires a non-self-consistent spin–orbit-coupling step, which is not covered here.}}

	== Magnon dispersion and exchange interactions ==		== Magnon dispersion and exchange interactions ==
	Scanning the spin-spiral energy ''E''('''q''') as in [[#Example 2: spin-spiral energy of a NiI2 monolayer\|Example 2]] is the basis of the ''frozen-magnon'' method for extracting magnetic interactions.{{cite\|marsman:prb:02}} Mapping the computed energies onto a classical Heisenberg model,		Scanning the spin-spiral energy ''E''('''q''') as in [[#Example 2: spin-spiral energy of a NiI2 monolayer\|Example 2]] is the basis of the ''frozen-magnon'' method for extracting magnetic interactions.{{cite\|marsman:prb:02}} Mapping the computed energies onto a classical Heisenberg model,

Huebsch at 13:35, 18 June 2026

2026-06-18T13:35:08Z

Show changes

← Older revision		Revision as of 11:55, 19 June 2026
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	This example uses a spin-spiral calculation to obtain the total energy of a flat spin spiral in a NiI<sub>2</sub> monolayer. The spin spiral is scanned along the {{TAG\|QSPIRAL}} path Γ–M–K–Γ to find the magnetic ground state. The triangular Ni sublattice is magnetically frustrated, which stabilizes an incommensurate spiral.		This example uses a spin-spiral calculation to obtain the total energy of a flat spin spiral in a NiI<sub>2</sub> monolayer. The spin spiral is scanned along the {{TAG\|QSPIRAL}} path Γ–M–K–Γ to find the magnetic ground state. The triangular Ni sublattice is magnetically frustrated, which stabilizes an incommensurate spiral.

	[[File:NiI2_spinspiral_structure.png\|thumb\|center\|~~650px~~\|~~Left: the 1T NiI<sub>2</sub> monolayer unit cell. Right: the~~ flat in-plane spin spiral at the computed Γ–M minimum '''Q''' = (0.214, 0, 0); the Ni moments rotate in the plane with period ''λ'' = 1/''Q'' ≈ 4.7 ''a~~'' along '''Q'~~''.]]		[[File:NiI2_spinspiral_structure.png\|thumb\|center\|600px\|The flat in-plane spin spiral at the computed Γ–M minimum '''Q''' = (0.214, 0, 0): the Ni moments rotate in the plane along '''Q''' with period ''λ'' = 1/''Q'' ≈ 4.7 ''a''.]]

	'''Structure''': A 1T (CdI<sub>2</sub>-type) NiI<sub>2</sub> monolayer, hexagonal ''a'' = 3.97 Å with ≈8 Å of vacuum ({{FILE\|POSCAR}}):		'''Structure''': A 1T (CdI<sub>2</sub>-type) NiI<sub>2</sub> monolayer, hexagonal ''a'' = 3.97 Å with ≈8 Å of vacuum ({{FILE\|POSCAR}}):

← Older revision		Revision as of 08:13, 22 June 2026
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	{{NB\|mind\| Symmetry:		{{NB\|mind\| Symmetry:

	The introduction of a spin spiral will lower the symmetry of the system. At present, VASP cannot correctly account for the presence of a spin spiral in its symmetry analysis. Therefore, the use of symmetry must be switched off in the subsequent steps by setting {{TAG\|ISYM\|-1}}. Generally, the number of irreducible '''k''' points changes for different symmetry settings ({{TAG\|ISYM}} and thus restarting from {{FILE\|CHGCAR}} should be preferred over restarting from {{FILE\|WAVECAR}}. You may set {{TAG\|LWAVE\|False}} to avoid writing the {{FILE\|WAVECAR}}. It is not advantageous to switch off symmetry from the get-go, as using symmetry reduces the computational effort and hence saves substantial computational cost during the course of convergence studies.}}		The introduction of a spin spiral will lower the symmetry of the system. At present, VASP cannot correctly account for the presence of a spin spiral in its symmetry analysis. Therefore, the use of symmetry must be switched off in the subsequent steps by setting {{TAG\|ISYM\|-1}}. Generally, the number of irreducible '''k''' points changes for different symmetry settings ({{TAG\|ISYM}}), and thus restarting from {{FILE\|CHGCAR}} should be preferred over restarting from {{FILE\|WAVECAR}}. You may set {{TAG\|LWAVE\|False}} to avoid writing the {{FILE\|WAVECAR}}. It is not advantageous to switch off symmetry from the get-go, as using symmetry reduces the computational effort and hence saves substantial computational cost during the course of convergence studies.}}
	{{NB\|tip\|Magnetism usually arises in d-electron and f-electron bands. To write the augmentation charges of those bands, set {{TAG\|LMAXMIX\|4}} (d electrons) or <code>6</code>.}}		{{NB\|tip\|Magnetism usually arises in d-electron and f-electron bands. To write the augmentation charges of those bands, set {{TAG\|LMAXMIX\|4}} (d electrons) or <code>6</code>.}}
	Choose the remaining electronic-minimization tags ({{TAG\|ALGO}}, {{TAG\|EDIFF}}, {{TAG\|NELM}}, {{TAG\|ISMEAR}}) as described in [[Setting up an electronic minimization]]; frustrated or incommensurate magnets often need a larger {{TAG\|NELM}} and {{TAG\|ALGO\|Conjugate}} is often most reliable.		Choose the remaining electronic-minimization tags ({{TAG\|ALGO}}, {{TAG\|EDIFF}}, {{TAG\|NELM}}, {{TAG\|ISMEAR}}) as described in [[Setting up an electronic minimization]]; frustrated or incommensurate magnets often need a larger {{TAG\|NELM}} and {{TAG\|ALGO\|Conjugate}} is often most reliable.
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	{{TAGBL\|ENCUT}} = 400		{{TAGBL\|ENCUT}} = 400

	Here, <tt>q1 q2 q3</tt> are the components of the spin-spiral propagation vector in direct (fractional) coordinates of the reciprocal lattice. In a spin-spiral calculation, the magnetic configuration is set both by the initial moments ''within'' the cell using the {{TAG\|MAGMOM}} tag, in the noncollinear (three-component-per-atom) format, and by how the magnetization rotates ''between'' cells (the {{TAG\|QSPIRAL}} vector). Worked examples are given in the [[#Examples\|Examples]] section below. Choose the remaining electronic-minimization tags as in step 1.		Here, <code>q1 q2 q3</code> are the components of the spin-spiral propagation vector in direct (fractional) coordinates of the reciprocal lattice. In a spin-spiral calculation, the magnetic configuration is set both by the initial moments ''within'' the cell using the {{TAG\|MAGMOM}} tag, in the noncollinear (three-component-per-atom) format, and by how the magnetization rotates ''between'' cells (the {{TAG\|QSPIRAL}} vector). Worked examples are given in the [[#Examples\|Examples]] section below. Choose the remaining electronic-minimization tags as in step 1.
	{{NB\|mind\|Symmetry must be switched off completely ({{TAG\|ISYM\|-1}}). VASP cannot account for the symmetry reduction introduced by a spin spiral, so leaving symmetry on produces incorrect results.}}		{{NB\|mind\|Symmetry must be switched off completely ({{TAG\|ISYM\|-1}}). VASP cannot account for the symmetry reduction introduced by a spin spiral, so leaving symmetry on produces incorrect results.}}
	{{NB\|tip\|Set {{TAG\|ENCUT}} (or equivalently {{TAG\|ENMAX}}) at least 100 eV above {{TAG\|ENINI}}. VASP prints a runtime warning if the value is too small for the chosen '''q''' vector, ''e.g.'':}}		{{NB\|tip\|Set {{TAG\|ENCUT}} (or equivalently {{TAG\|ENMAX}}) at least 100 eV above {{TAG\|ENINI}}. VASP prints a runtime warning if the value is too small for the chosen '''q''' vector, ''e.g.'':}}
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	{{TAGBL\|RWIGS}} = <one radius per species>		{{TAGBL\|RWIGS}} = <one radius per species>

	This switches on the [[I_CONSTRAINED_M\|constrained-magnetic-moment approach]] but sets the penalty potential to zero ({{TAG\|LAMBDA}} = 0.0). The magnetization density is then integrated inside site-centered spheres of radius {{TAG\|RWIGS}}, and the resulting local moments are written under <tt>M_int</tt> in the {{FILE\|OSZICAR}} file, ''e.g.'':		This switches on the [[I_CONSTRAINED_M\|constrained-magnetic-moment approach]] but sets the penalty potential to zero ({{TAG\|LAMBDA}} = 0.0). The magnetization density is then integrated inside site-centered spheres of radius {{TAG\|RWIGS}}, and the resulting local moments are written under <code>M_int</code> in the {{FILE\|OSZICAR}} file, ''e.g.'':

	E_p = 0.00000E+00 lambda = 0.000E+00		E_p = 0.00000E+00 lambda = 0.000E+00
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	{{NB\|tip\|The exact position of the incommensurate minimum depends on the [[XC functional]], [[Choosing pseudopotentials\|PAW potentials]], and proper convergence of k-mesh density, and cutoff energy.}}		{{NB\|tip\|The exact position of the incommensurate minimum depends on the [[XC functional]], [[Choosing pseudopotentials\|PAW potentials]], and proper convergence of k-mesh density, and cutoff energy.}}
	== Magnon dispersion and exchange interactions ==		== Magnon dispersion and exchange interactions ==
	Scanning the spin-spiral energy ''E''('''q''') as in [[#Example 2: ~~spin~~-spiral energy of a NiI2 monolayer\|Example 2]] is the basis of the ''frozen-magnon'' method for extracting magnetic interactions.{{cite\|marsman:prb:02}} Mapping the computed energies onto a classical Heisenberg model,		Scanning the spin-spiral energy ''E''('''q''') as in [[#Example 2: Spin-spiral energy of a NiI2 monolayer\|Example 2]] is the basis of the ''frozen-magnon'' method for extracting magnetic interactions.{{cite\|marsman:prb:02}} Mapping the computed energies onto a classical Heisenberg model,

	:<math> E({\bf q}) = E_0 - \sum_{\bf R} J({\bf R})\, \cos({\bf q}\cdot{\bf R}), </math>		:<math> E({\bf q}) = E_0 - \sum_{\bf R} J({\bf R})\, \cos({\bf q}\cdot{\bf R}), </math>
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	{{TAG\|LNONCOLLINEAR}}, {{TAG\|MAGMOM}}, {{TAG\|ISYM}}, {{TAG\|I_CONSTRAINED_M}}, {{TAG\|LAMBDA}}, {{TAG\|RWIGS}}, {{TAG\|LORBIT}}		{{TAG\|LNONCOLLINEAR}}, {{TAG\|MAGMOM}}, {{TAG\|ISYM}}, {{TAG\|I_CONSTRAINED_M}}, {{TAG\|LAMBDA}}, {{TAG\|RWIGS}}, {{TAG\|LORBIT}}

	{{TAG\|LSPIRAL}}, {{TAG\|QSPIRAL}}, {{TAG\|LZEROZ}}, , {{TAG\|ENINI}}		{{TAG\|LSPIRAL}}, {{TAG\|QSPIRAL}}, {{TAG\|LZEROZ}}, {{TAG\|ENINI}}

	== References ==		== References ==

← Older revision		Revision as of 09:45, 19 June 2026
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	=== Step 1: Start from a converged magnetic state ===		=== Step 1: Start from a converged magnetic state ===
	Begin with a converged collinear or noncollinear ground-state calculation of the primitive cell, following [[Setting up an electronic minimization]], and keep the resulting {{FILE\|CHGCAR}} as a starting point for the spin-spiral run. The total energy and on-site magnetic moments ({{TAG\|LORBIT}}) should be converged with respect to '''k'''-mesh density and energy cutoff ({{TAG\|ENCUT}}).		Begin with a converged collinear or noncollinear ground-state calculation of the primitive cell, following [[Setting up an electronic minimization]], and keep the resulting {{FILE\|CHGCAR}} as a starting point for the spin-spiral run. The total energy and on-site magnetic moments ({{TAG\|LORBIT}}) should be converged with respect to '''k'''-mesh density and energy cutoff ({{TAG\|ENCUT}}).
			{{NB\|mind\| Symmetry:

	The introduction of a spin spiral will lower the symmetry of the system. At present, VASP cannot correctly account for the presence of a spin spiral in its symmetry analysis. Therefore, the use of symmetry must be switched off in the subsequent steps by setting {{TAG\|ISYM\|-1}}. Generally, the number of irreducible '''k''' points changes for different symmetry settings ({{TAG\|ISYM}} and thus restarting from {{FILE\|CHGCAR}} should be preferred over restarting from {{FILE\|WAVECAR}}. You may set {{TAG\|LWAVE\|False}} to avoid writing the {{FILE\|WAVECAR}}. It is not advantageous to switch off symmetry from the get-go, as using symmetry reduces the computational effort and hence saves ~~substential~~ computational cost during the course of convergence studies.		The introduction of a spin spiral will lower the symmetry of the system. At present, VASP cannot correctly account for the presence of a spin spiral in its symmetry analysis. Therefore, the use of symmetry must be switched off in the subsequent steps by setting {{TAG\|ISYM\|-1}}. Generally, the number of irreducible '''k''' points changes for different symmetry settings ({{TAG\|ISYM}} and thus restarting from {{FILE\|CHGCAR}} should be preferred over restarting from {{FILE\|WAVECAR}}. You may set {{TAG\|LWAVE\|False}} to avoid writing the {{FILE\|WAVECAR}}. It is not advantageous to switch off symmetry from the get-go, as using symmetry reduces the computational effort and hence saves substantial computational cost during the course of convergence studies.}}
			{{NB\|tip\|Magnetism usually arises in d-electron and f-electron bands. To write the augmentation charges of those bands, set {{TAG\|LMAXMIX\|4}} (d electrons) or <code>6</code>.}}
	Magnetism usually arises in d-electron and f-electron bands. To write the augmentation charges of those bands, set {{TAG\|LMAXMIX\|4}} (d electrons) or <code>6</code>.

	Choose the remaining electronic-minimization tags ({{TAG\|ALGO}}, {{TAG\|EDIFF}}, {{TAG\|NELM}}, {{TAG\|ISMEAR}}) as described in [[Setting up an electronic minimization]]; frustrated or incommensurate magnets often need a larger {{TAG\|NELM}} and {{TAG\|ALGO\|Conjugate}} is often most reliable.		Choose the remaining electronic-minimization tags ({{TAG\|ALGO}}, {{TAG\|EDIFF}}, {{TAG\|NELM}}, {{TAG\|ISMEAR}}) as described in [[Setting up an electronic minimization]]; frustrated or incommensurate magnets often need a larger {{TAG\|NELM}} and {{TAG\|ALGO\|Conjugate}} is often most reliable.

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	The energy is lowest for an incommensurate spin spiral, not for the ferromagnet (Γ) or the high-symmetry M and K points, reflecting the frustration of the triangular Ni sublattice. Two shallow minima appear along inequivalent in-plane directions — near '''q''' ≈ (0.21, 0, 0) along Γ–M and '''q''' ≈ (0.13, 0.13, 0) along Γ–K — separated by a barrier of only ≈1 meV, and the spiral is stabilized by ≈16 meV per formula unit relative to the ferromagnet. The Γ–M minimum at '''q''' ≈ (0.21, 0, 0) is in good agreement with the helimagnetic propagation vector '''q''' = (0.220, 0, 0) measured for monolayer NiI<sub>2</sub> by spin-polarized scanning tunneling microscopy.{{cite\|miao:pnas:25}}		The energy is lowest for an incommensurate spin spiral, not for the ferromagnet (Γ) or the high-symmetry M and K points, reflecting the frustration of the triangular Ni sublattice. Two shallow minima appear along inequivalent in-plane directions — near '''q''' ≈ (0.21, 0, 0) along Γ–M and '''q''' ≈ (0.13, 0.13, 0) along Γ–K — separated by a barrier of only ≈1 meV, and the spiral is stabilized by ≈16 meV per formula unit relative to the ferromagnet. The Γ–M minimum at '''q''' ≈ (0.21, 0, 0) is in good agreement with the helimagnetic propagation vector '''q''' = (0.220, 0, 0) measured for monolayer NiI<sub>2</sub> by spin-polarized scanning tunneling microscopy.{{cite\|miao:pnas:25}}
	{{NB\|tip\|The exact position of the incommensurate minimum depends on the [[XC functional]], [[PAW potentials]], and proper convergence of k-mesh density, and cutoff energy.}}		{{NB\|tip\|The exact position of the incommensurate minimum depends on the [[XC functional]], [[Choosing pseudopotentials\|PAW potentials]], and proper convergence of k-mesh density, and cutoff energy.}}
	== Magnon dispersion and exchange interactions ==		== Magnon dispersion and exchange interactions ==
	Scanning the spin-spiral energy ''E''('''q''') as in [[#Example 2: spin-spiral energy of a NiI2 monolayer\|Example 2]] is the basis of the ''frozen-magnon'' method for extracting magnetic interactions.{{cite\|marsman:prb:02}} Mapping the computed energies onto a classical Heisenberg model,		Scanning the spin-spiral energy ''E''('''q''') as in [[#Example 2: spin-spiral energy of a NiI2 monolayer\|Example 2]] is the basis of the ''frozen-magnon'' method for extracting magnetic interactions.{{cite\|marsman:prb:02}} Mapping the computed energies onto a classical Heisenberg model,
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	== Related tags and articles ==		== Related tags and articles ==
	[[Spin spirals]], [[Setting up an electronic minimization]]		[[Spin spirals]] (Theory), [[Setting up an electronic minimization]]

	{{TAG\|LNONCOLLINEAR}}, {{TAG\|MAGMOM}}, {{TAG\|ISYM}}, {{TAG\|I_CONSTRAINED_M}}, {{TAG\|LAMBDA}}, {{TAG\|RWIGS}}, {{TAG\|LORBIT}}		{{TAG\|LNONCOLLINEAR}}, {{TAG\|MAGMOM}}, {{TAG\|ISYM}}, {{TAG\|I_CONSTRAINED_M}}, {{TAG\|LAMBDA}}, {{TAG\|RWIGS}}, {{TAG\|LORBIT}}