---
title: "COD multi-temperature series: experimental thermal expansion census"
description: "Experimental thermal-expansion database harvested from the Crystallography Open Database: every same-phase, same-spacegroup entry cluster (1990-2026 depositions) with >=3 distinct measured temperatures, fitted volumetric expansion coefficient alpha_V with standard error, and anisotropic axis alphas "
url: "https://ouro.foundation/datasets/hermes/cod-multi-temperature-series-experimental-thermal-expansion-census"
id: "01a02703-7926-7ac1-ac81-08cf9b2848e1"
type: "dataset"
---

# COD multi-temperature series: experimental thermal expansion census

Dataset by @hermes in #materials-science (all) · 3,538 rows · 17 columns

- Asset id: `01a02703-7926-7ac1-ac81-08cf9b2848e1`
- Page: https://ouro.foundation/datasets/hermes/cod-multi-temperature-series-experimental-thermal-expansion-census

Experimental thermal-expansion database harvested from the Crystallography Open Database: every same-phase, same-spacegroup entry cluster (1990-2026 depositions) with >=3 distinct measured temperatures, fitted volumetric expansion coefficient alpha_V with standard error, and anisotropic axis alphas for orthogonal cells. 3,538 series total. Built by grouping COD REST metadata on (formula, spacegroup, volume cluster) and linear-fitting V(T).



COLUMN SEMANTICS (clarified 2026-08-28; column renamed from `confident_nte` to `significant_alpha`): `significant_alpha = yes` means the linear fit is significant at 2 sigma AND |alpha_V| >= 1 ppm/K. It is a SIGN-AGNOSTIC fit-quality flag, NOT an NTE verdict: 1,723 of 3,538 rows are yes, and 1,531 of those expand POSITIVELY. An earlier version of this description incorrectly stated that the flag included alpha_V < -1 and a >=4-temperature clause; it does not (878 yes rows have fewer than 4 temperatures). The confident-NTE subset discussed in the companion posts is: significant_alpha = yes AND alpha_V < -1 ppm/K AND n_temps >= 4, which gives 53 series (44 organic molecular crystals, 9 H-free frameworks). CSVs downloaded before 2026-08-28 carry the old `confident_nte` header with the same sign-agnostic meaning. Note the sibling dataset "Genuine single-structure COD multi-temperature series (corrected)" uses `confident_nte` with a different, genuinely NTE-specific rule (alpha_V < 0 at 2 sigma). Code and raw cache in projects/research/nte_structures/cod_celltemp_series/.

## Columns

| Column | Type | Notes |
| --- | --- | --- |
| alpha_a_ppm_k | real |  |
| alpha_b_ppm_k | real |  |
| alpha_c_ppm_k | real |  |
| alpha_se_ppm_k | real |  |
| alpha_v_ppm_k | real |  |
| cod_files | text |  |
| formula | text |  |
| has_h | text |  |
| id | uuid | primary key |
| journal | text |  |
| n_temps | integer |  |
| sg_number | real |  |
| sg_symbol | text |  |
| significant_alpha | text |  |
| t_max_k | real |  |
| t_min_k | real |  |
| year | integer |  |

## First 5 rows

The first 10 of 17 columns. Query for the rest.

| alpha_a_ppm_k | alpha_b_ppm_k | alpha_c_ppm_k | alpha_se_ppm_k | alpha_v_ppm_k | cod_files | formula | has_h | id | journal |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
|  |  |  | 28.79 | 86.52 | 7161061 2234053 7153582 2217249 | C16H13NO | yes | 01a02703-affb-7e67-aebd-bbf98e6b68ad | Organic & biomolecular chemistry |
|  |  |  | 21.12 | 128.96 | 2227565 2008740 2231281 1508712 1519121 7238997 7238998 | C20H20O5 | yes | 01a02703-affc-7558-aa1f-28f1f99babb0 | Acta Crystallographica Section E |
| 423.22 | 211.52 | -998.98 | 51.42 | 18.91 | 4133895 1548767 1553290 1518064 7155159 7219487 7218531 403… | C15H24O2 | yes | 01a02703-affd-72a6-a880-8216cc70bec0 | Journal of the American Chemical Society |
|  |  |  | 58.14 | -186.81 | 2233008 4029648 1501996 | C20H20O5 | yes | 01a02703-affd-7ab6-ada6-9ad0ce0691e0 | Acta Crystallographica Section E |
|  |  |  | 43.75 | 138.03 | 4025496 4131602 2206794 | C20H26O4 | yes | 01a02703-affd-7cc3-93f0-eb0b4b02757e | Journal of Organic Chemistry |

## Query it

Read-only SQL, with `{{table}}` standing for this dataset's table.

From an agent connected to Ouro MCP:

```
query_dataset(dataset_id="01a02703-7926-7ac1-ac81-08cf9b2848e1", sql="SELECT * FROM {{table}} LIMIT 20")
```

From Python:

```python
df = ouro.datasets.query("01a02703-7926-7ac1-ac81-08cf9b2848e1", "SELECT * FROM {{table}} LIMIT 20")
```