---
name: "clag"
section: "1"
platform: "linux"
package: "psi3"
version: "3.4.0-6+b3"
release: "Debian 12 (Bookworm)"
platforms: ["linux"]
url: "https://new.carta.tech/clag"
---

# clag(1)

**NAME**      **clag - Lagrangian Program written in C.**

**DESCRIPTION**

The program **clag**      **forms the lagrangian matrix from the one and two particle density** **matrices and the one and two electron integrals.  The lagrangian** **is used for MCSCF and CI derivative calculations.**

**REFERENCES**

Lagrangian:

1\. A New Dimension to Quantum Chemistry, Y. Yamaguchi, Y. Osamura,  J.D. Goddard, H. F. Schaefer III, Oxford Univ. Press, (1994).

```
input.dat	Input file
FILE71	Transformed one-electron integrals
FILE72	Transformed two-electron integrals
FILE73	One-Particle Density Matrix
FILE74	Two-Particle Density Matrix
```

```
FILE75   Lagrangian
output.dat
```

**INPUT FORMAT**

The input for this program is read from the file input.dat. The following keywords are valid:

**PRINT =** *integer* This option determines the verbosity of the output.  A value of 0 prints nothing, a value of 1 prints calculated ci energy and the various components of the ci energy, a value of 2 prints the one- and two-electron contributions to the MO lagrangian as well as the MO lagrangian, a value of 3     prints the one-particle density matrix, and a value of 4 prints the two-particle density matrix.  Do not use print = 4 unless the test case is very small.

**WRITE\_CAS\_FILES =** *boolean* If TRUE, then write out the following files in canonical form (p\>=q, r\>=s, pq\>=rs) in Pitzer order: one-electron integrals (file81), two-electron integrals (file82), one-particle density matrix (file83), two-particle density matrix (file84), lagrangian (file85).  This is temporary and is intended to aid in linking DETCI with CASSCF.