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Computational Chemistry: Basis Shell Cartesian Spherical Count Tool

Count Cartesian or real spherical Gaussian basis functions for one explicit angular-momentum shell, without contractions, spin doubling or a molecular basis inventory.

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Description

Return functions in one angular-momentum shell.

Computational chemistry separates composition and electron bookkeeping from basis conventions, coordinates, quadrature and energetic weights. A local exact count or unit conversion can be consistent without identifying a valid electronic state, optimized structure or normalized thermodynamic ensemble.

Return functions in one angular-momentum shell.

When to use this tool

Use Computational Chemistry: Basis Shell Cartesian Spherical Count when checking a supplied computational-chemistry count, coordinate, basis or weighting convention.

How to use the tool and how it works

  1. Enter angularMomentum, convention. Use the units and conventions below.
  2. Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
  3. Read result. Expand result to inspect the returned fields.

Return functions in one angular-momentum shell. Require angularMomentum l in [0,32] and convention cartesian or spherical; count is (l+1)*(l+2)/2 or 2*l+1 respectively.1

Input fieldMeaning and unitsAccepted input
angularMomentumAngular MomentumRequired. Safe integer.
conventionConventionRequired. Text; one of "cartesian", "spherical". Implementation limit: 8192 Unicode code points and 16384 UTF-16 code units.
Output fieldInterpretationReturned shape
resultReturned calculated value or nested object under the stated output convention.Required. Object.
result.functionCountFunction CountCalculated result member: number.
json
{
  "input": {
    "angularMomentum": 2,
    "convention": "cartesian"
  },
  "output": {
    "result": {
      "functionCount": 6
    }
  }
}

Limitations and assumptions

  • This counts one shell's angular components; contractions, primitives and actual basis-library definitions are not included.
  • Outputs are nested inside result. Inputs must satisfy both the field types and the cross-field conditions above. Invalid input causes an error; a successful false flag or documented placeholder is a different result.
  • Numeric calculations use binary floating point unless exact decimal-integer arithmetic is explicitly stated. No hidden measurement tolerance or decimal rounding is added; nonfinite or out-of-contract results are rejected. Numeric signed-zero results are exported as zero.

Alternative or Complementary methods

Use a complete verified electronic-structure or statistical-mechanical model and compatible property/unit conventions for actual molecular inference.

References

  1. Calculation and input contract: computational-chemistry/basis-shell-cartesian-spherical-count — tool.io

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