Source: https://guthlabs.ai/docs/instruments/phase-diagram-lever-rule-calculator/implementation/

instrument implementation / implementation-contract

# Phase Diagram Lever Rule Calculator implementation

A source-bound implementation contract for Phase Diagram Lever Rule Calculator; deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**Lifecycle: **implementation-contract**

## Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

**Record owner**: Guth Instruments

**Lifecycle**: verified-clean

**Evidence ID**: t7-044

**Effect**: Computation or source lookup only

## Input and validation requirements

The formula produces an undefined 0/0 result when C_L equals C_alpha, and naive application outside the two-phase interval produces nonphysical fractions below zero or above one. Reversing endpoint or composition-axis conventions can also silently swap phase labels.

## Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

## Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

````
{
  "inputs": {
    "system": "Pb-Sn",
    "temperature_C": 182.99,
    "overall_composition_wt_percent_Sn": 61.9,
    "phase_field": "alpha+beta",
    "C_alpha_wt_percent_Sn": 18.3,
    "C_beta_wt_percent_Sn": 97.8
  },
  "expected_outputs": {
    "phase_fractions": {
      "alpha": 0.451572327,
      "beta": 0.548427673
    },
    "sum": 1
  },
  "reference_data": {
    "eutectic_temperature_C": 183,
    "eutectic_composition_wt_percent_Sn": 61.9,
    "C_alpha_wt_percent_Sn_at_eutectic": 18.3,
    "C_beta_wt_percent_Sn_at_eutectic": 97.8,
    "source_convention": "Widely tabulated standard value; ASM Alloy Phase Diagrams textbook compilation"
  },
  "working": "Use the α+β lever rule. Denominator = Cβ − Cα = 97.8 − 18.3 = 79.5 wt% Sn. Alpha fraction = (Cβ − C0)/(Cβ − Cα) = (97.8 − 61.9)/79.5 = 35.9/79.5 = 359/795 = 0.451572327. Beta fraction = (C0 − Cα)/(Cβ − Cα) = (61.9 − 18.3)/79.5 = 43.6/79.5 = 436/795 = 0.548427673. Check: 0.451572327 + 0.548427673 = 1.000000000."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/phase-diagram-lever-rule-calculator/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/phase-diagram-lever-rule-calculator/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/phase-diagram-lever-rule-calculator/qualification/>)

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json`

- `evidence-tranche7/tranche7-results.json`