## mowindow

Enable the selective perturbation (SP) approach introduced in the context of RT-TDSCF in Kadek et al. *PCCP* **17**, 22566 (2015) but applicable to CPP calculations as well. SP enables to represent the perturbation and response operators only in selected molecular orbitals, allowing thus to eliminate nonphysical excitations that are artifacts of the finite basis representation in core-level spectroscopies.

**Input block**

**Extended variant**

`mowindow:`

`occupied: [intial-mo-index] - [final-mo-index]`

`virtual: [intial-mo-index] - [final-mo-index]`

**Default**

`none`

**Example**

```
mowindow:
occupied: 4-6
```

```
mowindow:
occupied: 7-10
virtual: 15-46
```

### Note

- By default, the entire orbital spectrum is considered.

- Occupied and virtual orbitals must be within their respective range. The range for occupied orbitals is from 1 to HOMO, whereas the range for virtual orbitals is from HOMO+1 to the total number of MOs.

### Tip

- SP turns out to be particularly useful for X-ray spectroscopies, where excitations occur only from specific core-shell orbitals. Here, we recommed to select for perturbation only the core-shell occupied MOs.

## transition-analysis

Enable the transition density matrix analysis (TDMA) introduced in the context of RT-TDSCF in Repisky et al. *JCTC* **11**, 980 (2015) but applicable to CPP calculations as well. TDMA enables to perform the orbital analysis of spectral transitions in RT-TDSCF simulations.

**Input block**

**Extended variant**

`transition-analysis:`

`occupied: [intial-mo-index] - [final-mo-index]`

`virtual: [intial-mo-index] - [final-mo-index]`

`threshold: [real]`

**Default**

`none`

**Example**

```
transition-analysis:
occupied: 8-10
virtual: 11-25
threshold: 1.0e-5
```

### Note

- By default, TDMA is disabled.

- Occupied and virtual orbitals must be within their respective range. The range for occupied orbitals is from 1 to HOMO, whereas the range for virtual orbitals is from HOMO+1 to the total number of MOs.

### Tip

- Since TDMA may lead to an extensive data printout, we recommend to select only those orbitals relevant for the spectroscopy of interest.

## xc

Specify details associated with the evaluation of the exchange–correlation (xc) kernel.

**Input block**

**Short variant**

```
xc:
[functional]
```

**Extended variant**

`xc:`

`functional: [functional]`

`noncollinearity: [string]`

**Default**

```
xc:
functional : from-scf
noncollinearity : v2019
```

**Example**

`xc: XALDA`

```
xc:
functional : XALDA
noncollinearity : v2005
```

### Warning

- The use of ALDA or XALDA options is not recommended, because they usually approximate the full xc kernel. Their use is only recommended when comparing the calculated data to implementations in other quantum chemistry programs, where those approximations can not be avoided.

## maxiterations

Define the maximum number of micro-iterations for the solver.

**Input line****Default**

```
maxiterations:
[integer]
```

`maxiterations: 30`

**Example**

`maxiterations: 50`

## checkpoint

Define the frequency of data checkpointing during the iterations.

**Input line****Default**

```
checkpoint:
[integer]
```

`checkpoint: 5`

**Example**

`checkpoint: 10`

## convergence

Define the convergence threshold for the CPP solver.

**Input line****Default**

```
convergence:
[real]
```

`convergence: 0.0001`

**Example**

`convergence: 1.0e-5`

### Note

- The quantity tested for convergence is the norm of the residue vector divided by the norm of the solution vector.

## frequencies

Specify the (angular) frequencies at which to solve the (damped) linear reponse equation.

**Input line****Default**

```
frequencies:
[real1 integer x real2]
```

`frequencies: 0.0`

**Example**

`frequencies: 0.0 50x0.07`

`frequencies: 0.2 0.5 0.6 1.00`

`frequencies: 0.2 0.5 0.6`

### Note

- The units for the frequencies are specified by the keyword units.

## damping

Specify the damping parameter for the damped linear reponse equation.

**Input line****Default**

```
damping:
[real]
```

`damping: 0.0`

**Example**

`damoing: 0.1`

### Note

- The units for the damping parameter are specified by the keyword units.

## Latest Publications

### Book chapter on relativistic real-time electron dynamics

### Book chapter on relativistic theory of EPR and (p)NMR

## Useful Links

## Our Contacts

Department of Chemistry

UiT The Arctic University of Norway

Tromsø, NO-9037 Norway

Email: info@respectprogram.eu