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Xuanyuan

Contents

  1. Xuanyuan
    1. General keywords
      1. Direct
      2. Schwarz
      3. Maxmem
      4. RS
      5. Scalar & Heff
      6. Soint & Hsoc
      7. Nuclear & Inuc
      8. Cholesky
    2. Expert keywords
      1. NoCheck
      2. NRDebug
      3. Keyword3
      4. Keyword4
  2. Depend Files
  3. Examples
  4. References

Xuanyuan is used to calculate one electron and two electron integrals. It is named after Chinese ancestor Xuanyuan Huangdi.

General keywords

Direct

Ask for integral direct calculations.

Schwarz

Used with direct, ask for Schwarz equality prescreening.

Examples: 

$xuanyuan
Direct
Schwarz
$end

Maxmem

Set maximum memory used in integral calculation. Unit can be MW and GW, i.e. Mega Words and Giga Words

Examples: 

$xuanyuan
Maxmem
  512MW
$end

RS

Examples: 

$xuanyuan
Rs
 0.33
$end

Scalar & Heff

Scalar is a keyword to turn on scalar relativistic effects using sf-X2C (Heff=3) by default.

Other options for Heff are (0, nonrelativistic; 1, sf-ZORA; 2, sf-IORA; 3/4, sf-X2C; 5, sf-X2C+so-DKH3 (spin-free); 21, sf-X2C; 22, sf-X2C with atom-block-diagonal X and full R (sf-X2C-aXR); 23, sf-X2C with atom-block-diagonal unitary transformation (sf-X2C-aU). Among these relativistic Hamiltonians, 21, 22, and 23 have analytic gradients and some one-electron properties (contact density at present in scf).

Examples: 

$xuanyuan
scalar
heff
3
$end

Soint & Hsoc

soint is a keyword to turn on soc integral calculations in post-SCF steps. Default option for hsoc is 0 (only 1e-soc int). The recommended option is 2 (so1e+somf2e).

Other options are used in soint_util/somf2e.F90 for choosing different combinations of so1e and mean-feild so2e (SOMF) operators.

0 so-1e

1 so-1e + somf (two-electron spin-orbit interaction is included via an effective fock operator)

2 so1e + somf-1c (one-center approximation to two-electron integrals)

3 so-1e + somf-1c / no soo (turn off spin-other-orbit contributions)

4 so-1e + somf-1c / no soo + WSO_XC (use dft xc functional as soo part)

5 so-1e + somf-1c / no soo + WSO_XC(-2x: following Neese's paper scale dft part by -2 to mimic soo part)

These options plus 10 gives the operators in BP approximations. In practice, hsoc=1 is the most accurate, and hsoc=2 is preferred for large molecules.

Note if heff=5, then the one-electron part will be calculated in xuanyuan and stored in disc for so-DKH3 type one-electron spin-orbit term. The accuracy of such operator requires further tests. }}} Examples: 

$xuanyuan
scalar
heff
3
soint
hsoc
2
$end

Nuclear & Inuc

Inuc defines the nuclear charge distribution used in the V and pVp integrals, which can be -1 for point charge model (debug only), 0 for point charge model (default), 1 for finite nucleus model by an s-type Gaussian function, and other finite nucleus models (N.Y.I.).

For Za < 110, the nuclear charge radii are taken from Ref.[Visscher1997] (in a.u).

For Za ≥ 110, the nuclear charge radius is 0.57 + 0.836 * A1/3 (in fm), where the isotope mass number A is estimated by Za according to the relationship A(Za) = 0.004467 * Za2 + 2.163 * Za - 1.168. See Appendix A in Ref.[Andrae2000] and Ref.[Andrae2002].

NOTE: the finite nucleus model has been implemented only in scalar calculations at present, but will be used in SOC calculations soon.

Cholesky

Examples: 

$xuanyuan
Cholesky
  S-CD 1.d-5
$end

Expert keywords

NoCheck

For Heff=21 only: check inverse variational collapse (IVC; see Ref.[Liu2007]). Stop (0; default) or not (1) in the case of IVC.

IVC may lead to numerical instability, which may be serious in geometry optimization.

NRDebug

In relativistic calculations, use a C-light of 10^8 to reproduce non-relativistic results (for debug only).

Keyword3

xxx

Keyword4

xxx

Depend Files

Filename

Description

Format

Examples

N.A.

References