Feos

- Python only: Release the changes introduced in `feos-core` 0.4.1 and `feos-dft` 0.4.1.

Changed
- Replaced some slow array operations to make calculations with multiple associating molecules significantly faster. [129](https://github.com/feos-org/feos/pull/129)

Fixed
- Fixed a regression introduced in [108](https://github.com/feos-org/feos/pull/108) that lead to incorrect results for the 3B association scheme. [#129](https://github.com/feos-org/feos/pull/129)

Added
- Added SAFT-VRQ Mie equation of state and Helmholtz energy functional for first order Feynman-Hibbs corrected Mie fluids. [79](https://github.com/feos-org/feos/pull/79)
- Added `estimator` module to documentation. [86](https://github.com/feos-org/feos/pull/86)
- Added benchmarks for the evaluation of the Helmholtz energy and some properties of the `State` object for PC-SAFT. [89](https://github.com/feos-org/feos/pull/89)
- The Python class `StateVec` is exposed in both the `feos.eos` and `feos.dft` module. [113](https://github.com/feos-org/feos/pull/113)
- Added uv-B3-theory and additional optional argument `virial_order` to uvtheory constructor to enable uv-B3. [98](https://github.com/feos-org/feos/pull/98)

Changed
- Export `EosVariant` and `FunctionalVariant` directly in the crate root instead of their own modules. [62](https://github.com/feos-org/feos/pull/62)
- Changed constructors `VaporPressure::new` and `DataSet.vapor_pressure` (Python) to take a new optional argument `critical_temperature`. [86](https://github.com/feos-org/feos/pull/86)
- The limitations of the homo gc method for PC-SAFT are enforced more strictly. [88](https://github.com/feos-org/feos/pull/88)
- Removed generics for units in all structs and traits in favor of static SI units. [115](https://github.com/feos-org/feos/pull/115)

Packaging
- Updated `pyo3` and `numpy` dependencies to 0.18. [119](https://github.com/feos-org/feos/pull/119)
- Updated `quantity` dependency to 0.6. [119](https://github.com/feos-org/feos/pull/119)
- Updated `num-dual` dependency to 0.6. [119](https://github.com/feos-org/feos/pull/119)


Fixed
- Fixed incorrect indexing that lead to panics in the polar contribution of gc-PC-SAFT. [104](https://github.com/feos-org/feos/pull/104)
- `VaporPressure` now returns an empty array instead of crashing. [124](https://github.com/feos-org/feos/pull/124)

- Major restructuring of the entire `feos` project. All individual models are reunited in the `feos` crate. `feos-core` and `feos-dft` still live as individual crates within the `feos` workspace.

Fixed
- Fixed a bug due to which the default ideal gas contribution was used for every equation of state. [17](https://github.com/feos-org/feos/pull/17)

Added
- Added [gc-PC-SAFT](https://github.com/feos-org/feos-gc-pcsaft) equation of state and Helmholtz energy functional.
- Added [PeTS](https://github.com/feos-org/feos-pets) equation of state and Helmholtz energy functional.
- Added [UV-Theory](https://github.com/feos-org/feos-uvtheory) equation of state for Mie fluids.

Changed
- Combined all equations of state into a single Python class `EquationOfState` and all Helmholtz energy functionals into the Python class `HelmholtzEnergyFunctional`. [11](https://github.com/feos-org/feos/pull/11)

Packaging
- Updated [`quantity`](https://github.com/itt-ustutt/quantity/blob/master/CHANGELOG.md) to 0.5.0.
- Updated [`feos-core`](https://github.com/feos-org/feos-core/blob/main/CHANGELOG.md) to 0.2.0.
- Updated [`feos-dft`](https://github.com/feos-org/feos-dft/blob/main/CHANGELOG.md) to 0.2.0.
- Updated [`feos-pcsaft`](https://github.com/feos-org/feos-pcsaft/blob/main/CHANGELOG.md) to 0.2.0.