高島千波(D2)が実装した2成分相対論のコードが最新版GAMESS（version July 31, 2022 R1）で公開されました。
主な実装は以下の4点です。
・無限次2成分相対論(IOTC)法の2電子項の追加：IOTC2E
・局所ユニタリー変換（LUT）-IOTCの2電子項の追加：LUTIOTC2
・相対論的DFT計算における描像変化補正（PCC）：PCCDFT

=====<<GAMESSマニュアルの抜粋>>======================

$RELWFN group

The pinnacle of this line is the local unitary transformation approximation to full IOTC (LUT-IOTC).
RELWFN=LUT-IOTC is the most numerically accurate and fastest running method for the one-electron term available, so the use of LUT-IOTC is recommended.

More accurate scalar relativistic treatment can be accomplished by including 2e-relativistic corrections by RELWFN=IOTC2E or LUTIOTC2.

For DFT calculations with RELWFN=IOTC, LUT-IOTC, IOTC2E, or LUTIOTC2, PCCDFT option is recommended (PCCDFT=.TRUE.)

* * * the next parameter is used with DFT:
PCCDFT = a flag to perform picture change corrected (PCC)
DFT of Y. Ikabata, T. Oyama, M. Hayami, J. Seino, and H. Nakai.
This option is valid for RELWFN=IOTC, LUT-IOTC, IOTC2E, and LUTIOTC2.
The default is .FALSE.

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参考文献

• “Implementation of picture change corrected density functional theory based on infinite-order two-component method to GAMESS program”
  C. Takashima, J. Seino, H. Nakai, J. Comput. Chem. Jpn., 19, 128-130 (2020).(日本コンピュータ化学会2020春季年会精選論文特集号)