Band-structure calculation using density-functional theory - Revision history

Huebsch: Add Category:Crystal momentum

2026-03-20T16:08:11Z

Add Category:Crystal momentum

← Older revision		Revision as of 16:08, 20 March 2026
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	[[Category:Band structure]]		[[Category:Band structure]]
	[[Category:Howto]]		[[Category:Howto]]
			[[Category:Crystal momentum]]

Liebetreu: /* Option A: Single run */

2026-03-20T12:26:03Z

Option A: Single run

← Older revision		Revision as of 12:26, 20 March 2026
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	=== Option A: Single run ===		=== Option A: Single run ===
	{{Available\|~~VASP~~ 6.3.0}}		{{Available\|6.3.0}}

	==== Step 1: Prepare SCF settings ====		==== Step 1: Prepare SCF settings ====

Huebsch: /* Step 4: Plot the band structure */

2026-03-19T15:55:28Z

Step 4: Plot the band structure

← Older revision		Revision as of 15:55, 19 March 2026
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	import py4vasp		import py4vasp
	calc = py4vasp.Calculation.from_path(".")		calc = py4vasp.Calculation.from_path(".")
	calc.band.plot("kpoints_opt")		ef = calc.dos.read()["fermi_energy"]
			calc.band.plot("kpoints_opt", fermi_energy=ef)
	</syntaxhighlight>		</syntaxhighlight>
	{{NB\|tip\|Set the {{TAG\|EFERMI}} tag or pass the Fermi energy explicitly, because {{py4vasp}} reads the Fermi energy from the KPOINTS_OPT density of states (<code>results/electron_dos_kpoints_opt/efermi</code>), which is computed from the line-mode '''k''' points and is therefore unreliable. ~~Use the Fermi energy from the SCF run instead:~~		{{NB\|tip\|Set the {{TAG\|EFERMI}} tag or pass the Fermi energy explicitly, because {{py4vasp}} reads the Fermi energy from the {{FILE\|KPOINTS_OPT}} density of states (<code>results/electron_dos_kpoints_opt/efermi</code>), which is computed from the line-mode '''k''' points and is therefore unreliable.\|:}}
	~~<syntaxhighlight lang="python">calc.band.plot("kpoints_opt", fermi_energy=...)</syntaxhighlight>~~\|:}}

	=== Option B: Split run ===		=== Option B: Split run ===

Huebsch: Option A Step 4: add EFERMI tip — kpoints_opt fermi_energy reads from line-mode DOS (unreliable), must use SCF Fermi energy

2026-03-19T15:51:17Z

Option A Step 4: add EFERMI tip — kpoints_opt fermi_energy reads from line-mode DOS (unreliable), must use SCF Fermi energy

← Older revision		Revision as of 15:51, 19 March 2026
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	calc.band.plot("kpoints_opt")		calc.band.plot("kpoints_opt")
	</syntaxhighlight>		</syntaxhighlight>
			{{NB\|tip\|Set the {{TAG\|EFERMI}} tag or pass the Fermi energy explicitly, because {{py4vasp}} reads the Fermi energy from the KPOINTS_OPT density of states (<code>results/electron_dos_kpoints_opt/efermi</code>), which is computed from the line-mode '''k''' points and is therefore unreliable. Use the Fermi energy from the SCF run instead:
			<syntaxhighlight lang="python">calc.band.plot("kpoints_opt", fermi_energy=...)</syntaxhighlight>\|:}}

	=== Option B: Split run ===		=== Option B: Split run ===

Huebsch: Move visualization code inline into Option A Step 4 and Option B Step 6; remove redundant Visualization section

2026-03-19T15:45:46Z

Move visualization code inline into Option A Step 4 and Option B Step 6; remove redundant Visualization section

@@ Line 25: / Line 25: @@
 ==== Step 4: Plot the band structure ====
-:[[#Visualization|Visualize the band structure]] using {{py4vasp}}.
+:{{py4vasp|url=calculation/band/#py4vasp.calculation._band.Band.to_graph}} provides utilities for plotting the band structure. Run the following in a Python notebook in the directory of the calculation:
 === Option B: Split run ===
@@ Line 69: / Line 74: @@
 ==== Step 6: Plot the band structure ====
-:[[#Visualization|Visualize the band structure]] using {{py4vasp}}.
+:{{py4vasp|url=calculation/band/#py4vasp.calculation._band.Band.to_graph}} provides utilities for plotting the band structure. Run the following in a Python notebook in the directory of the calculation:
 == Choosing a high-symmetry path ==
@@ Line 97: / Line 109: @@
 The empty lines and labels are optional and meant for readability. The labels will be used by {{py4vasp}}. VASP produces equidistant '''k''' points for each segment. The example above would yield 10 points from ''L'' to ''Γ'', 10 points from ''Γ'' to ''X'', 10 from ''X'' to ''U'', and 10 from ''K'' to ''Γ'', including endpoints.
 For further details and instructions, please consult the section on [[KPOINTS#Band-structure_calculations|band-structure calculations in the KPOINTS]] documentation.
 == Recommendations and advice ==

Huebsch at 15:32, 19 March 2026

2026-03-19T15:32:25Z

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	~~These~~ step-by-step instructions cover calculating the ~~'''~~[[:Category:Band structure\|band structure]]~~'''~~ within density-functional theory (DFT) including references to practical examples.		The step-by-step instructions below cover calculating the [[:Category:Band structure\|band structure]] within density-functional theory (DFT), including references to practical examples.

	Obtaining the band structure involves first solving the Hamiltonian to get eigenvalues and eigenvectors, then plotting them as electronic energy levels versus [[crystal momentum]]. The Kohn-Sham (KS) Hamiltonian requires at least the density (charge and possibly magnetization) and may contain higher derivatives depending on the [[:Category:Exchange-correlation functionals\|exchange-correlation (XC) functional]].		Obtaining the band structure involves first solving the Hamiltonian to get eigenvalues and eigenvectors, then plotting them as electronic energy levels versus [[crystal momentum]]. The Kohn-Sham (KS) Hamiltonian requires at least the density (charge and possibly magnetization) and may contain higher derivatives depending on the [[:Category:Exchange-correlation functionals\|exchange-correlation (XC) functional]].
	{{NB\|mind\| The approach presented on this page applies to [[GGA#Available functionals\|LDA]] (needs density), [[GGA\|GGA]] (needs density and gradient) and deorbitalized meta-GGA (needs density, gradient and Laplacian) functionals. Additionally, it can be used for [[METAGGA\|meta-GGAs]] that need the kinetic energy density as of VASP 6.6.0. In contrast, another approach is required [[Band-structure calculation using hybrid functionals\|for computing the band structure for hybrid functionals]] and [[Band-structure calculation using hybrid functionals\|for computing the band structure for MGGAs before VASP 6.6.0]].}}		{{NB\|mind\| The approach presented on this page applies to [[GGA#Available functionals\|LDA]] (needs density), [[GGA\|GGA]] (needs density and gradient), and deorbitalized meta-GGA (needs density, gradient, and Laplacian) functionals. Additionally, it can be used for [[METAGGA\|meta-GGAs]] that need the kinetic energy density as of VASP 6.6.0. In contrast, another approach is required [[Band-structure calculation using hybrid functionals\|for computing the band structure for hybrid functionals]] and [[Band-structure calculation using hybrid functionals\|for computing the band structure for MGGAs before VASP 6.6.0]].}}

	== Step-by-step instructions ==		== Step-by-step instructions ==
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	==== Step 1: Prepare SCF settings ====		==== Step 1: Prepare SCF settings ====

	:Follow [[Setting_up_an_electronic_minimization#Create_the_input_files\|the steps to create input files]] on the instructions for [[setting up an electronic minimization]]. Typically, this ~~results in~~ defining the input settings using the {{FILE\|INCAR}} ~~file~~, {{FILE\|POSCAR}} ~~file~~, {{FILE\|KPOINTS}} ~~file~~, and ~~the~~ {{FILE\|POTCAR}} ~~file~~.		:Follow [[Setting_up_an_electronic_minimization#Create_the_input_files\|the steps to create input files]] on the instructions for [[setting up an electronic minimization]]. Typically, this involves defining the input settings using the {{FILE\|INCAR}}, {{FILE\|POSCAR}}, {{FILE\|KPOINTS}}, and {{FILE\|POTCAR}} files.

	==== Step 2: High-symmetry path ====		==== Step 2: High-symmetry path ====

Huebsch at 15:30, 19 March 2026

2026-03-19T15:30:32Z

Show changes

Huebsch: Style fixes: meta-opener, & to and, ICHARG|11, backup->back up, p4vasp typo, passive->active voice, uncomment categories, add references, anchor link spaces, KPOINTS section link

2026-03-19T13:10:05Z

Style fixes: meta-opener, & to and, ICHARG|11, backup->back up, p4vasp typo, passive->active voice, uncomment categories, add references, anchor link spaces, KPOINTS section link

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Huebsch: Huebsch moved page Construction:Band-structure calculation using DFT to Band-structure calculation using density-functional theory without leaving a redirect

2026-03-19T12:57:22Z

Huebsch moved page Construction:Band-structure calculation using DFT to Band-structure calculation using density-functional theory without leaving a redirect

← Older revision	Revision as of 12:57, 19 March 2026
(No difference)

Liebetreu: /* Visualization */

2026-03-17T15:27:14Z

Visualization

← Older revision		Revision as of 15:27, 17 March 2026
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	However, if using {{FILE\|KPOINTS_OPT}} for the high-symmetry path ('''[[#Option A: Single run \|Option A: Single run]]'''), you need to pass "kpoints_opt" as an argument to <code>calc.band.plot</code>:		However, if using {{FILE\|KPOINTS_OPT}} for the high-symmetry path ('''[[#Option A: Single run \|Option A: Single run]]'''), you need to pass "kpoints_opt" as an argument to <code>calc.band.plot</code>:
	<syntaxhighlight lang="python">calc.band.plot("kpoints_opt")</syntaxhighlight>		<syntaxhighlight lang="python">calc.band.plot("kpoints_opt")</syntaxhighlight>
	~~Conversely, if~~ using '''[[#Option B: Split run \|Option B: Split run]]''' and not setting {{TAG\|EFERMI}} in Step 5, you can still change the Fermi energy at the plotting stage:		{{NB\|mind\| If using '''[[#Option B: Split run \|Option B: Split run]]''' and not setting {{TAG\|EFERMI}} in Step 5, you can still change the Fermi energy at the plotting stage:
	<syntaxhighlight lang="python">calc.band.plot(fermi_energy=...) # plug in extracted Fermi energy from SCF run</syntaxhighlight>		<syntaxhighlight lang="python">calc.band.plot(fermi_energy=...) # plug in extracted Fermi energy from SCF run</syntaxhighlight>}}

	== Recommendations and advice ==		== Recommendations and advice ==