The schema is schema/Potentials.capnp, a vendored copy of the shared potentials-schema release pinned in subprojects/potentials-schema.wrap. This page lists the fields that decide what CPMD computes. The option mapping lists every typed field with its feature ID and deck spelling.

CPMDParams

Field	Type, default	Role
functional	Text, "BLYP"	functional when no dft section sets one
cutOffRy	Float64, 70.0	plane-wave cutoff in Rydberg when no system section sets one
charge	Int32, 0	system charge when the system section does not set one
multiplicity	Int32, 1	2S+1; above 1 selects spin-polarized defaults
task	Text, "gradient"	host hint: energy, gradient, md, optimize
title	Text	comment header of the rendered deck
memoryMb	UInt32, 0	host memory hint
scratchDir, permanentDir	Text	FILEPATH in &CPMD, and the working directory for RESTART.1, LATEST, GEOMETRY, and GEOMETRY.xyz; permanentDir wins
cpmdRoot	Text	OpenCPMD tree hint for hosts
enginePath	Text	library path hint for hosts such as rgpot
inputBlocks	List(Text)	literal &SECTION ... &END blocks placed before the rendered sections
inputSections	List(CPMDInputSection)	structured sections, rendered in list order

A section missing from inputSections gets a default: &CPMD with OPTIMIZE WAVEFUNCTION and CONVERGENCE ORBITALS 1e-6, &SYSTEM with SYMMETRY 0, ANGSTROM, and the top-level cutoff, charge, and multiplicity, and &DFT with the top-level functional.

CPMDInputSection

A union; each list entry sets exactly one arm.

Arm	Payload	Renders
cpmd	CPMDCpmdSection	&CPMD
system	CPMDSystemSection	&SYSTEM
dft	CPMDDftSection	&DFT
atoms	CPMDAtomsSection	&ATOMS without coordinates
vdwParams, propParams, linresParams, pimdParams, pathParams, tddftParams, respParams, exteParams, vectorsParams	typed long-tail sections	the matching section
atom, basis, clas, eam, exte, hardness, info, linres, molstates, mts, nlcc, path, pimd, potential, prop, ptddft, resp, tddft, vdw, vectors, wavefunction	CPMDDirectiveSection: directives and nested subsections	the matching section, one line per directive
set	CPMDSetDirective: key = "SECTION.KEYWORD", value	one keyword merged into a named section
generic	CPMDGenericSection: name, directives	a section by name
raw	Text	a full &SECTION ... &END block, verbatim

CPMDDirective

Field	Meaning
keyword	the line, for example "PCG MINIMIZE"
args	List(Text); each entry becomes one indented line below the keyword

Every typed section has a directives list for keywords without a typed field.

CPMDCpmdSection, the fields a force call uses

Field	Default	Deck
optimizeWavefunction	true	OPTIMIZE WAVEFUNCTION
convergenceOrbitals	1e-6	CONVERGENCE ORBITALS
maxIter	0, omitted	MAXITER; the OpenCPMD path inserts 40 when absent
maxStep	0, omitted	MAXSTEP, the geometry step limit of CPMD’s own drivers
odiis, odiisVectors, odiisOptions	off	ODIIS and its vector count
pcg	off	PCG; PCG MINIMIZE goes in directives
diis	off	DIIS
centerMoleculeOff, centerMoleculeOn	off	CENTER MOLECULE OFF / ON
restartWavefunction	off	RESTART WAVEFUNCTION; read on the cold first call only
isolatedMolecule	off	ISOLATED MOLECULE

The OpenCPMD path ignores restarted coordinates, velocities, and geometry: the host owns them.

CPMDSystemSection, the fields that set the cell

Field	Default	Deck
symmetry	0	SYMMETRY; 0 is isolated
angstrom	true	ANGSTROM, the unit of CELL and &ATOMS
cell	empty	CELL: six values a, b/a, c/a, cos(alpha), cos(beta), cos(gamma), or nine with cellVectors
cellAbsolute, cellDegree, cellVectors	off	CELL ABSOLUTE, DEGREE, VECTORS
cutOffRy	70.0	CUTOFF
poissonSolver, poissonParameter	empty	POISSON SOLVER; SYMMETRY 0 without one adds HOCKNEY
charge, multiplicity	0, 1	CHARGE, MULTIPLICITY
kpointsMonkhorstPack	empty	KPOINTS MONKHORST-PACK

CPMDDftSection

Field	Default	Deck
functional	"BLYP"	FUNCTIONAL
lsd	false	LSD
gcCutoff	0, omitted	GC-CUTOFF
oldCode, newCode	off	OLDCODE / NEWCODE
hfx, hfxScreening	off	hybrid exchange controls

CPMDAtomsSection and CPMDAtomsPseudopotential

Field	Default	Deck
element		element symbol, such as "Si"
path		the *file line, a library name or a path
lmax, loc, skip	-1, omitted	LMAX=, LOC=, SKIP=; 0 is S, 1 P, 2 D, 3 F
kleinmanBylander	false	KLEINMAN-BYLANDER on the *file line
raggio	0, omitted	RAGGIO=
nonlinearCore	false	NLCC

The atoms section also carries constraints, isotopes, velocities, dummyAtoms, changeBonds, generate, and directives. Coordinates never go here. On the OpenCPMD path, the &ATOMS block CPMD reads is rebuilt from each step’s geometry. Entries in pseudopotentials supply the file, LMAX, LOC, and KLEINMAN-BYLANDER for the elements they name. Elements left out of that list use a built-in table for H, C, N, O, Si, and Ge; see writing a CPMDParams message.

ForceInput

Field	Default	Meaning
pos		3 * natoms coordinates in lengthUnit
atmnrs		atomic numbers
box	empty	nine values, row-major cell vectors in lengthUnit
lengthUnit	"angstrom"	unit of pos and box
energyUnit	"eV"	unit of the PotentialResult energy

PotentialConfig

A union of backend arms plus a common overlay (CommonMethodSpec). cpmdc accepts the cpmd arm, which holds a CPMDParams, or the overlay alone; see the C ABI reference for the lowering rules.