# SIESTA-LINRES

Development of DFPT within SIESTA

## Blueprint information

- Status:
- Not started

- Approver:
- None

- Priority:
- Undefined

- Drafter:
- Miguel Pruneda

- Direction:
- Needs approval

- Assignee:
- SIESTA-LINRES

- Definition:
- Approved

- Series goal:
- None

- Implementation:
- Unknown

- Milestone target:
- None

- Started by

- Completed by

### Related branches

### Related bugs

### Sprints

### Whiteboard

Implementation of DFPT within SIESTA. As opposed to initial LINRES project, DFPT will not be a post-processing tool, but will be performed within the siesta run.

-First, standard DFT ground-state calculation with SCF loop in SIESTA, to determined rho0

- Secondly, apply perturbation that correspond to a displacement of a specific atom (the 3 spatial directions are computed on the fly). For each "atomic displacement":

* SCF loop that determines: (1) perturbed Hamiltonian $\delta H$, (2) perturbed density matrix ($\delta\

* From $\delta\rho^{SCF}$" one can compute a whole row of the Dynamical Matrix.

Initially, only perturbation that correspond to atomic displacements. Other perturbations might be considered, but "atomic displacements" are more difficult because they include Pulay-like corrections.